Using flavors from Roles

-flavors defined in roles are now written into parameters that
 are fed to heat
-association for image name and flavor param are stored in
 template tools by hard, for Icehouse
-exceptions for processing stack erros set to 400
-fixed docs of the helper functions

Change-Id: I0e3e8dcd78a36fc1e008eedfa6ec793015e3ac1e
Merge "Using flavors from Roles"