increment group counters when a user is created
decrease user count in affected groups after user delete
increase/decrease everyone count on user creation/deletion
avoid global selector
fixing JS synatx errors
remove the group in case the last user has removed from that group
magic strings - bad kungfu
some more cleanup
use .filterAttr()
use .filterAttr()
Merge pull request #9525 from owncloud/incrementuser2

increment/decrement group and user counts when necessary