Update 0.13.4

This is mainly a graphics update that introduces fog and volumetric lighting to the game, which makes it quite a bit prettier to look at.
There are also some smaller bug fixes and UI changes.

FIXES:
- Newly bought traps lost their highlighted grid if in level countdown
- A description box with bad text could appear in hero selection
- Electrum spazzed out if locked onto an enemy entering a portal
- Reset pickup counter correctly between games

ADDITIONS:
- Fog effect (togglable in video settings)
- Volumetric lights (togglable in video settings)
- Setting for disabling mandatory help texts
- Pulsing effect on "Create character" button when starting with a new hero

BALANCE:
- Level 8 is now just a little easier