REFACTORING: Compiles and runs (still some fixes needed)

Doubleclicking with mouse doesn't work anymore and is disabled.
FleetManager -class is to be added and some functionality will
be moved there.
UI: Added toolbar buttons for painting walls, POIs and startpoint

* Mainwindow now includes toolbar buttons for different drawing and
selection actions
* Walls, POIs and startpoint is also selectable, movable and removable
* Added qresource file to include graphics
REFACTORING: Fixed (FleetManager class still missing)