front: Remove audio resampling preference (always trivial).

Developers and experts can still set this by editing mupen64plus.cfg if
they really have to.
front: Allow experts to override some settings in config file.

Anything we explicitly specify in NativeConfigFiles.java cannot be
overridden by manually editing the mupen64plus.cfg file.  So generally
the only things we should ever explicitly write to file are

 - settings that are exposed via the main menu interface (i.e. anything
   in UserPrefs.java)
 - settings that should never be changed manually (i.e. anything in
   AppData.java, hard-coded file paths, settings required for Android
   that differ from upstream defaults)

Otherwise, we should just allow the native core/plugin code to write
the default values specified by upstream.

TODO:
 - AutoStateSlotIncrement: Either expose this in the main menu, or
   remove the forced setting in NativeConfigFiles.java
 - Figure out the dependencies between Rice's TextureEnhancement and
   TextureEnhancementControl settings
 - Identify any other Rice settings that should be forced explicitly in
   NativeConfigFiles.java (OpenGLRenderSetting, AnisotropicFiltering,
   etc.)
 - Consider removing more Rice settings from the front menu
front: Delete mupen config file when resetting preferences.

Should safeguard against noobs accidentally borking the config file.