cleanup 0500s, #1170
cleanup 0500s, #1170

- they all have on/off switches
- dxr no longer exists: update URL
- don't recommend users delete files
   - saves two lines
   - they poses zero threat (they have prefs)
   - deleting them can causes unwanted console errors/noise
ghacksuserjs/ghacks-user.js,ghacksuserjs/ghacks-user.js