Improvement of selection feature

* Use defined hook for range selection instead of currently first element in map
* Allow toggle of selection elements by ctrl
* Allow single element toggle
* Don't let right-click context destroy the selection
* Added workaround for broken gtk cursor methods

Change-Id: Ie3ac11c5834d517249b238bf17f77296dc9e993a
Usage of constant as proposed by S.Lohse.

Change-Id: I8b547dcf84f6bb0e9db4ac7e7448ddf6bc58c954