This pull request enables new group widgets

[Altonss]

This is just a draft because after a group widget is created, the group doesn't open up. Instead just the last window of the app opens. The group id is well transfered with the intent to the MainActivity, but then I don't really know how to do ^^ I'm sure it's a not a very difficult fix, but for the moment I'm stuck. This would fix this feature request: #397