Applied fixes #95, #75, #90, Turkish language etc

+ Fix: When new user has joined to the system, in the group pages he is
shown as a member of croups where there are no members.
+ Feature: Add manager info to user
+ Fix: When user changes language, then xml:lang="et-ee" lang="et-ee"
are not changed in index.php
+ Feature: invitation sending added an option to send out plain text or
html
+ Applied Feature: Turkish language pack
+ Applied Fix: Allow invite to user with email containing + sign #95
+ Applied Fix: User added to a group during invite, should be
automatically added to the group #73
+ Applied Fix: Successful registration should be properly redirected #73
+ Applied Fix: New registered user has shown as a member of some groups
#90