System and board settings enhancements

[jaw-sh]

General

• Board and site settings will default to the default value set in the option (as intended), but saving these options will write the default option as a hard value which does not flex with modified defaults. Settings should be modified so that default values are not written as a setting whenever possible.
• Site settings are not accessible from the global scope and require a controller for no real reason.

Fixes

• Due to prior limitation, there are certain ## TODO ## items that are implementations of options which were not done because settings were not in global scope.
  • Attachment filesize
  • Thumbnail size

New Settings

• Option to autoprune stored IPs.
• Option for filename syntax.