Installation Quick Start Section (CDAP-695)

• Add an installation quick-start section. (Fixes https://issues.cask.co/browse/CDAP-695)
Staged: http://stg-web101.sw.joyent.continuuity.net/cdap/2.6.0-SNAPSHOT-2.6.0_doc_updates/en/admin-manual/installation/quick-start.html
• Add to installation index page.
Staged: http://stg-web101.sw.joyent.continuuity.net/cdap/2.6.0-SNAPSHOT-2.6.0_doc_updates/en/admin-manual/index.html
• Re-arrange installation guide to flow better.
• Improve progress messages from build script.
• Add "Removing an Application" to the getting-started section.

Staged at: http://stg-web101.sw.joyent.continuuity.net/cdap/2.6.0-SNAPSHOT-2.6.0_doc_updates/en/admin-manual/index.html

There may be additional cdap-site.xml properties that need flagging for the quick-start guide. If you know of any, please suggest in the comments.
*when logged in as the "cdap" user?  

This paragraph is kinda wierd how it switches from cdap to hbase.  FYI the original reason for the link to the HBase guide was its description on what is needed in general to get any user-specified ulimits working on Ubuntu.