Reimplement Menu item to hide object selection outlines for 2.0

Adds an option to the Build->Options menu which make it possible to hide the selection highlights while building. This is of great use while using very small prims, or aligning textures. Also alleviates the massive drop in frame rate when manipulated large link sets.

Reimplemented the 2.0 way rather than using the old patch, as it's much cleaner than the old way.