Limit FPS in editor

Add an Editor Preferences option to limit the global FPS (only in the editor).

Additionally(optionally) add support for the following:
-Limit FPS in editor viewport used as editor.
-Limit FPS in editor viewport used as play in editor (same could be used for client and other play windows).

Reason: Save energy(battery life), Nvidia coil whine.
Personally I could live with 30 fps in the editor but I want at least 60 when play testing.

Note: t.MaxFPS typed in manually is working, but ConsoleVariables.ini [Startup] t.MaxFPS is not and I wasn’t able hack around it. Anyhow this is such a basic feature it should be available in Editor Preferences.

Limiting FPS in Nvidia Control Panel is not a viable workaround as it will limit the total FPS shared among windows, e.g. testing with 3 clients with an FPS limit of 60 each window “gets” only 20 FPS.