Add Mists of Pandaria Compatibility & Stability Fixes

[HoliestWoW]

This pull request resolves issues for users on Mists of Pandaria clients (Interface 50500) and fixes several critical startup bugs.

Key Changes:

• Mists of Pandaria Support: The addon now works with the Mists of Pandaria version of the game.
• Monk Class: Added support for the Monk class, so the addon won't cause errors for them.
• Updated Dungeon List: Updated the dungeon list to include all MoP dungeons and raids with their correct max levels in the "Rules" tab.
• Bug Fixes: Fixed several major bugs that could cause the addon to break or fail to load when starting up the game.
• Code Cleanup: Cleaned up and organized the addon's internal files. This should make it run more smoothly and will make future updates easier.

This update should make the addon stable and fully functional for MoP players.