[0.2.7] Bugfixes & Resolutions support

Hi !

In this update, I focused on fixing issues and trying to make the game playable on most aspect ratios.

Fixes :

• The enemies would freak out when the FPS are low. This was due to the enemies movements being calculated every frames and when there wasn't enough of them the zombies couldn't move properly.

• I remade ALL of the UI to be responsive and adapt to the users resolution (this was a huge pain, my fault)

• Added an FPS counter so you can see how badly optimized it is.
• Fixed changing time speed while in paused time.