PermissionSelectionPartial: check provided permission to specify if user is able to make changes

[mmnosek]

Permission selection partial should have the ability to receive permission to check when a user is making any changes. Now changes are not secured by any permission.

Don't have an idea how to do it yet, just placed it here to remember in the future.

[mmnosek]

Current idea is to pass permission through the constructor (optionally). Permission should be checked before every PermissionSelectionPartial handler execution.

[mmnosek]

@joozek78 we need to think about that topic. For SWE project it's required to limit groups adding/deleting only to children of current user groups. I remember our talk about a flexible solution, so that's why I don't want to implement it on my own.

[mmnosek]

Added here: 1d44aa8