Add documentation for Savanna

 * Reference Architecture page has a short description of what Savanna is +
   current limitations
 * Post-Deployment Check has new section 'Platform Tests Description' which
   currently lists prerequsites for Savanna tests run
Added Savanna test cases details
Incorporated SvetlanaS feedback
Merge pull request #26 from mattymo/refactor-3.2

Refactor 3.2 for features and wording
Merge pull request #29 from dmitrymex/master

Add documentation for Savanna
fixed image background, removed the TM sign from 'Fuel'
Merge pull request #30 from SvetlanaS/oct13

fixed image background, removed the TM sign from 'Fuel'
murano docs and 3.2 relase notes

more wording fixes

trimmed down health checks

updated Murano wording