More or less a hotfix with a little new addition!

• Added the store upgrade system: I prepared the framework for future store upgrades that can be unlocked from the 'My Store' screen on the computer. Right now, the only available upgrade is the automatic door opener and closer.
• Bugfix: Your hand has returned to you. I wonder where it was...
• Bugfix: Lights don't spawn on the roof anymore when they are packaged up
• Bugfix: Sometimes at the end of the day, the pause menu would lock the player, without saving the game. My bad.