Add a mouse position directive

This PR suggests adding a mouse position directive that wraps an ol3 mouse position control.

Currently we call $scope.$apply, and therefore incur an Angular digest cycle, on each mousemove. That's bad. This PR fixes it.

The code is currently incomplete. It misses the part that watches the mousePositionProjection property and calls setProjection on the control. We need https://github.com/openlayers/ol3/pull/688 for that.

This PR currently includes the commits of the dev_makefile branch. I will rebase the dev_mousepositioncontrol if we decide to reject dev_makefile (#18). See https://github.com/geoadmin/mf-geoadmin3/compare/dev_makefile...dev_mousepositioncontrol for the actual diff.