User share document setting field while joining group

[Daniel Zoller]

Add field to the user for "user shares documents with the group" while joining group

[Thomas Niebler]

This should be deactivated by default. At least, this is the current behaviour.

[Thomas Niebler]

This should basically just be a concatenation of two updateGroup actions. GUI elements are missing, but this feature is of minor importance, since the default behaviour is "no sharing in groups" for new users.

[Mario Holtmüller]

Users now have the possibility to mark a checkbox during the join process to share their documents with the group.

I'm not sure if a info-text should be added that states that sharing is only possible if the group has sharing enabled?!