0.5.6B - Improvements and clay pit bug fix

Change log 0.5.6B

Improvements
- Can now click ESC to cancel any selection (replaced hotkey for opening menu)
- Technology researched message will not show if Technology Tree is opened, but a researched technology sound will still play to indicate researched technology while Technology Tree is opened
- Opening Technology Tree will close researched technology message automatic
- Removed Quit Game button from in-game menu since it was often confused with the Main Menu button

Balance changes
- You no longer have to produce Copper Helmet before producing Bronze Shield
- You no longer have to produce Copper Helmet before producing Bronze Armor

Bug fixes
- Fixed wrong textures for Clay Pit during different gathering stages