Enable end-conversation by swipe gesture

Add EnhancedListView library de.timroes.android:EnhancedListView:0.3.4
to enable swipe-out for ListViews

Re-enable selectableItemBackground

Dont end selectedConversation on swipe

Call mConversationFragment.reinit() instead.
Add separate undo string for swipe MUC.

Add blacklistedConversation for undo swipe

Update title_undo_swipe_* strings

Fix undo(), rename blacklistedConversation

Fix discardUndo(); re-init selectedConversation

maintain scroll position after undo

clear notification when dismissing a conversation

modified / simplified maintain scroll position code

simplify handling of selectedConversation

change undo_muc string, remove notifyDataSetChanged()