Add Developers Map in About dialog
[developers map] change tilelayer to openstreetmap
switch to the first tab in about dialog
Reset rotation on new project

Closes http://hub.qgis.org/issues/11832
Disable support for canvas rotation by default

Rotation support can be enabled at runtime exporting the
QGIS_ENABLE_CANVAS_ROTATION variable (set to any value)
[developers map] add to popup whether developer is committer
Merge pull request #1634 from slarosa/usermap_about

Adds Developers Map in About dialog