Clarifications to OpenStack gaps

I've made the following changes:
  - removed the direct references to Mitaka release, as this analyzis
might be updated to later releases.
  - Added the relevant OpenStack projects to the table
  - Made some clarifications to the existing gaps
  - Removed the "Is available in Mitaka" as none of them are avaiable ;)

Change-Id: I48a4695de8e3d72b7fbcd2287d62b4b178758051
Signed-off-by: csatari <gergely.csatari@nokia.com>