The Android manifest contains a lot of unnecessary permissions. We need to get rid of them.

Right now, the only "invasive" permission we need is the "Calendar R/W" permission for fedocal to operate. On Android 6+, this is handled automatically - the user is asked the permission whenever they try to add an event to their calendar.

Apart from that, we need access to the internet, device ID, app-local data and a couple of other harmless permissions.