Block Edit Modes
In order to make the blocks more flexible, introduce new edit modes settable by environments admins. So it's necessary to introduce a new option in blocks edition, only accesible by environments admins, to set one of the followings edit modes:
- Can edit and move (DEFAULT)
- Can edit but not move
- Can not edit or move
It's usefull for templates creation to define which and how blocks can be changed.
This will also replace the old "fixed" option