Fixed Hotkey for controlling background preview.

Adding a new property that take note of both boolean WatchEscapeIsDown and CanNavigateBackground for the hit test of the "Watch3DView".
Removed preview from nodes that are not suppose to have preview.
Merge pull request #730 from l2obin/HotkeyFixesBranch

Fixed Hotkey for controlling background preview.
Merge pull request #731 from SkyApple/RemovingPreviewFromSpecificNodes_ChocoButterUI

Removed preview from nodes that are not suppose to have preview.
Merge branch 'master' into ChocoButterUI