Missing validation for environment name in API

Add environment name validation to API so that when names are entered
by user via the murano client CLI they get validated in the same way
they do via the murano dashboard UI, i.e., name must contain only
alphanumeric or "_-." characters, must start with alpha. If not valid,
raise an exception with a 400 error.

Change-Id: Ib125e017acbdd6b6881ec705763c17170b80e44b
Closes-Bug: 1373045
Merge "Missing validation for environment name in API"