Merge pull request #13 from dvicini/master

Some overall work to get users integrated
Merge pull request #14 from dvicini/master

added friends
ActionBarTabs in InvitationBase class
ActionBarTabs, InvitationBase class plus subshells
Merge branch 'master' of https://github.com/ese-unibe-ch/ese2013-team6
Merge pull request #15 from dvicini/master

invitations (partly)
More GUI shell, need to commit for pulling
Merge branch 'master' of https://github.com/ese-unibe-ch/ese2013-team6

Conflicts:
	src/MensaUniBe/res/values/strings.xml
Merge pull request #16 from dvicini/master

now user can download invitations he received (Inbox) and invitations he...
need to pull
Merge pull request #17 from dvicini/master

Friend requests working