Revert "add "3dmode" action to cycle between 3d modes"

This reverts commit 2c2ee42dd742195a6e5c649f938294438d08b4ec.
[3D] add a global toggle to enable/disable stereoscopic related features and moved interaction with stereoscopic related settings to a central stereoscopics manager
[3D] renamed "3D" labeled settings to "stereoscopic" (mode3d -> stereoscopicmode)
[3D] observe changes to the stereoscopicmode setting and push changes to the GraphicContext instead of having the context constantly checking the setting
[3D] add cActions to cycle through stereo modes and toggle it on/off
[3D] move stereomode detection from filename to stereoscopicsmanager and make the flags configurable via advanced settings.
[3D] add stereoscopic mode "mono" (2D)
[3D] add stereo mode info to stream details and make it available to skins via the GUIInfoManager
[3D] add GUI stereoscopic mode to GUIInfoManager to have it available in skins
[3D] add settings to configure the playback behavior of stereoscopic videos

- preferred playback mode of stereoscopic movies (ask, stereoscopic/3D, mono/2D)
- preferred stereoscopic mode (use video mode or a fixed mode)
- quit stereoscopic mode when playback stopped
[3D] add cAction to select stereoscopic mode from a list
[3D] add cAction to toggle between stereoscopic/3D and mono/2D mode
[3D] turn off stereoscopic mode on startup
[3D] add stereo mode popup to Confluence similar to the subtitle popup
[Experimental] don't trigger a skin reload but only a reload of fonts

Because the skin reload is a little show stopper we should try to avoid it. IIRC the reason for it was ugly font rendering in stereoscopic modes if not done. This commit tries to compensate that by only reloading the fonts but not the skin.