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] turn off stereoscopic mode on startup
[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 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