Add default CSS style for mouse position

Missing CSS was confirmed with issue #680, this commit is to fix it and change
ol-mouse-position class to ol-mouseposition. I choose for the moment the top
right corner to display the coordinates from mouse position control because of
potential conflict with the scaleline control.
Merge pull request #687 from fredj/geolocation

Use ol.projection.identityTransform instead of goog.functions.identity
Merge pull request #691 from elemoine/mouseposition

Add default CSS for mouse position control
Redefine ol.Pixel to be Array.<number>