ConversationFragment: enable back button to dismiss

The ConversationFragment has a AlertDialog for showing the message
details, which sets the cancelable property to be false. This stops the
user from being able to use the back button to dismiss the dialog.
Merge pull request #1053 from shenki/master

ConversationFragment: enable back button to dismiss message detail dialog
Moved colors to the right place.
Closes #913: Message ID is -1 when called in aggregate
Merge pull request #1069 from phenx-de/color-cleanup

Moved colors to the right place.
Give user the opportunity to chose no LED-notification.
Mark message details on pending messages as such.

Closes #1034
Format-neutral compare numbers in MMS group with local device.

Closes #1018
upgrade gradle version
// FREEBIE
added Google Play Store text