actualize highscore with more fitting points
add difficulty level according to score and fix hp bar bug

* change enemy strength and number of enemies dependent on score
* change item amount dependent on score
* add push traverser for player and level collision
add collision with walls and fix weapon bugs

* add push collider to keep player out of walls
* fix weapon z-order
* change weapon displayed on hud whith weapon change
add level borders and make level scale larger
fix weapon bug
add function to change displayed weapn on the hud