Don't clear startup-cache by default for restart menu-item

[MrOtherGuy]

Clearing startup-cache can have unforseen consequences especially regarding mv3 extensions.

Possibly the clearest way is to create a duplicate menuitem which says to restart and clear startup-cache. But this needs some thought.

[MrOtherGuy]

This was fixed some time ago in 9e105f6 and there are now two separatr menuitems in tools menu.

For future work, it may still be necessary to add some further tweaks because modifying scripts generally required clearing startup-cache, but doing that might mess up suspendable mv3 event pages.