First spring demo update

I've started to fix the bugs that have been reported on the demo. Here what should be fixed for now :

Fixes :

1. Some survivors not dying when asked to.

2. The player suddenly getting up when crawling into a vent.

3. Lack of a death trigger that resulted in an infinite fall.

4. Fixed some crates that were not spawning their loot.

5. Several optimization fixes.

6. Fixed the speed of how texts are displayed.

Balance :

• Grenades and some enemies now do less damages.

• Less probability for the enemies to throw a grenade.

• Enemies are now more prone to be staggered.

Feature :

• You can now skip the intro.

• Added a Quicksave/Quickload option (F5/F7, binds can be changed in the option).

• Added an antosave feature.

• Added color to some text to make some tutorials more obvious.

• Now the game saves the state of most of the animated objects (ie: you can save while on a lift or a moving platform).

• The SMG wielding enemies shooting animation are more obvious, they really aim at you.

Thank you for playing the game. There is still a lot of work for me to do but seeing how much people liked the demo (even though there's a lot a bugs) motivates me to get something really great out.