Add 'restart editor' popup when changing 'enable UV from hit result'

The Support UV From Hit Results flag in Project Settings does not take effect until the user restarts the editor. Enabling this doesn't let the user know that they have to restart the editor.

1. Launch QAGame in editor.
2. Open the level TraceUVTest (under Developers/jamesgolding/maps).
3. Click on Edit > Project Settings.
4. Click on Physics in the side panel.
5. Enable Support UV From Hit Result.
6. Play in viewport.
7. Hover the reticule over the barrel and press O.

RESULT:

Nothing happens. The setting doesn't take effect until the editor restarts.

EXPECTED:

User is prompted to restart the editor to enable the feature.