Allow for admins to change a user's theme.

I implemented a theme I'm having work done on, and then disabled it, it's still set as my theme for my account, despite it not being the default theme, and unless i re-enable the theme and change it manually, I'm stuck using the theme.

There should be a setting to force all users to use the default theme or perhaps an admin setting within editing a member to manually choose which theme they use.