Make a better UI in-game

[LoicCK]

The UI right now is kind of lame. Simple texts, hideous buttons...

The goal would be to have a nice, coherent, pleasant UI. This would need to be implemented in different places.

• Decide on the assets / style of the UI
• Implement it in-game (gold and health counter)
• Implement it in different screens (title, options...)
• Implement in the new inventory Better inventory UI #4