Merge pull request #30 from dvicini/master

small bug fixes: spinner in action bar now hides when going to map and social manager invite lists are never null
Merge pull request #31 from dvicini/master

fixed registration bug hopefully?
createInvitationFragments is involved
Merge branch 'master' of https://github.com/ese-unibe-ch/ese2013-team6
small Improvements of Usability
new Lister added
datahandler now receives responses