Update Alpha 1.15

- Skills tweaks and changes

• Tweaked the MP usage for all the skills that are using MP
• The MP usage is now dependent on each skill level, not the player's, as it was initially
• Reordered some elements from the skills menu for a better look

- Slightly changed the design of some areas

- Improved the "cave effect" for the certain areas

- Changed monsters' defense formula (it should take less time now to actually deal damage to bigger monsters)

- Added an "extra reward" for the first mission

- Some other small bug fixes, including several misplaced layers