[SPARK-5608] Improve SEO of Spark documentation pages

- Add meta description tags on some of the most important doc pages
- Shorten the titles of some pages to have more relevant keywords; for
  example there's no reason to have "Spark SQL Programming Guide - Spark
  1.2.0 documentation", we can just say "Spark SQL - Spark 1.2.0
  documentation".

Author: Matei Zaharia <matei@databricks.com>

Closes #4381 from mateiz/docs-seo and squashes the following commits:

4940563 [Matei Zaharia] [SPARK-5608] Improve SEO of Spark documentation pages

docs/_layouts/global.html

@@ -7,7 +7,9 @@
         <meta charset="utf-8">
         <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
         <title>{{ page.title }} - Spark {{site.SPARK_VERSION_SHORT}} Documentation</title>
-        <meta name="description" content="">
+        {% if page.description %}
+          <meta name="description" content="{{page.description | replace: 'SPARK_VERSION_SHORT', site.SPARK_VERSION_SHORT}}">
+        {% endif %}
 
         {% if page.redirect %}
           <meta http-equiv="refresh" content="0; url={{page.redirect}}">

docs/bagel-programming-guide.md

@@ -1,6 +1,7 @@
 ---
 layout: global
-title: Bagel Programming Guide
+displayTitle: Bagel Programming Guide
+title: Bagel
 ---
 
 **Bagel will soon be superseded by [GraphX](graphx-programming-guide.html); we recommend that new users try GraphX instead.**

docs/configuration.md

@@ -1,6 +1,7 @@
 ---
 layout: global
-title: Spark Configuration
+displayTitle: Spark Configuration
+title: Configuration
 ---
 * This will become a table of contents (this text will be scraped).
 {:toc}

docs/graphx-programming-guide.md

@@ -1,6 +1,8 @@
 ---
 layout: global
-title: GraphX Programming Guide
+displayTitle: GraphX Programming Guide
+title: GraphX
+description: GraphX graph processing library guide for Spark SPARK_VERSION_SHORT
 ---
 
 * This will become a table of contents (this text will be scraped).

docs/index.md

@@ -1,6 +1,8 @@
 ---
 layout: global
-title: Spark Overview
+displayTitle: Spark Overview
+title: Overview
+description: Apache Spark SPARK_VERSION_SHORT documentation homepage
 ---
 
 Apache Spark is a fast and general-purpose cluster computing system.

docs/mllib-decision-tree.md

@@ -1,7 +1,7 @@
 ---
 layout: global
-title: Decision Tree - MLlib
-displayTitle: <a href="mllib-guide.html">MLlib</a> - Decision Tree
+title: Decision Trees - MLlib
+displayTitle: <a href="mllib-guide.html">MLlib</a> - Decision Trees
 ---
 
 * Table of contents

docs/mllib-guide.md

@@ -1,6 +1,8 @@
 ---
 layout: global
-title: Machine Learning Library (MLlib) Programming Guide
+title: MLlib
+displayTitle: Machine Learning Library (MLlib) Guide
+description: MLlib machine learning library overview for Spark SPARK_VERSION_SHORT
 ---
 
 MLlib is Spark's scalable machine learning library consisting of common learning algorithms and utilities,

docs/monitoring.md

@@ -1,6 +1,7 @@
 ---
 layout: global
 title: Monitoring and Instrumentation
+description: Monitoring, metrics, and instrumentation guide for Spark SPARK_VERSION_SHORT
 ---
 
 There are several ways to monitor Spark applications: web UIs, metrics, and external instrumentation.

docs/programming-guide.md

@@ -1,6 +1,7 @@
 ---
 layout: global
 title: Spark Programming Guide
+description: Spark SPARK_VERSION_SHORT programming guide in Java, Scala and Python
 ---
 
 * This will become a table of contents (this text will be scraped).

docs/quick-start.md

@@ -1,6 +1,7 @@
 ---
 layout: global
 title: Quick Start
+description: Quick start tutorial for Spark SPARK_VERSION_SHORT
 ---
 
 * This will become a table of contents (this text will be scraped).

docs/security.md

@@ -1,6 +1,7 @@
 ---
 layout: global
-title: Spark Security
+displayTitle: Spark Security
+title: Security
 ---
 
 Spark currently supports authentication via a shared secret. Authentication can be configured to be on via the `spark.authenticate` configuration parameter. This parameter controls whether the Spark communication protocols do authentication using the shared secret. This authentication is a basic handshake to make sure both sides have the same shared secret and are allowed to communicate. If the shared secret is not identical they will not be allowed to communicate. The shared secret is created as follows:

docs/sql-programming-guide.md

@@ -1,6 +1,7 @@
 ---
 layout: global
-title: Spark SQL Programming Guide
+displayTitle: Spark SQL Programming Guide
+title: Spark SQL
 ---
 
 * This will become a table of contents (this text will be scraped).

docs/streaming-programming-guide.md

@@ -1,6 +1,8 @@
 ---
 layout: global
-title: Spark Streaming Programming Guide
+displayTitle: Spark Streaming Programming Guide
+title: Spark Streaming
+description: Spark Streaming programming guide and tutorial for Spark SPARK_VERSION_SHORT
 ---
 
 * This will become a table of contents (this text will be scraped).

docs/tuning.md

@@ -1,6 +1,8 @@
 ---
 layout: global
-title: Tuning Spark
+displayTitle: Tuning Spark
+title: Tuning
+description: Tuning and performance optimization guide for Spark SPARK_VERSION_SHORT
 ---
 
 * This will become a table of contents (this text will be scraped).