Clearing installed server content does not clear the `UserData` directory

[ike709]

OpenDream stores server-specific cached data in subdirectories of RT's IResourceManager.UserData. Using the Clear installed server content button in the launcher does not clear this data.

This seems like an oversight, since I expected this button to clear everything.

[PJB3005]

Blanket clearing this folder would delete user preferences and such which is obviously not desirable. The button is meant for download cache.

If we want to fix this, we should add a separate cache folder as available to the game, and then have it clear that folder too.