Main entry point for all the manageboards admin screens.

• In 1.0.x, the manage_boards permission is required to access this section
• In 1.1 no permission is needed to access this function but all sub-actions except settings require the manage_boards permission
• The settings sub-action (1.1 only) requires the admin_forum permission
• Part of the manage_boards adminIndex
• Loads the ManageBoards language file
• Calls the appropriate function based on the sub-action
• Checks to make sure you have permission to access the specified sub-action
• Doesn't display the Settings option if you can't access it