Improve YAQL documentation for YAQL

YAQL currently has very scarce documentation, which might prevent new users from getting involved. With the release of 1.0.0 version it's time to fix this

Improve behaviour of environments in "Delete FAILURE" state for Murano

Delete FAILURE is a dangerous state of environment. Currently this means that some error occurred either during destroy() method of some classes deployed, or stack was not deleted correctly or the app for one of the packages in the env was deleted. In most of those cases this might leave environment and stack in in...