Multiview: support cltr+click rename for non left/right views
Multiview: fix for crash when stereo was off
Multiview: refactor of UV/Image editor and image flags

* showing 3d only when image is 3d and show 3d is on
* improve logic in 3dview to only handle 3d when in camera
* setting show_stereo as default mode for image editor
* image and Imageuser flags re-arranged
* image IMA_IS_STEREO flag set when opening image =)

* missing: rendered image needs to be tagged as IMA_IS_STEREO too
* also in some cases I need to force to see a different render layer to
  get everything working