Adds Flavor ID validations

* Flavor ID should not contain special symbols.
* Flavor ID should be in range 1-255 characters.
* Flavor ID should not have leading/trailing whitespaces.

Fixes LP Bug 1202136
DOCIMPACT

Change-Id: I63c36811a57982e826f22f827f86d40ff6a6210e
Merge "Adds Flavor ID validations"