Many changes

GUI crosshair added
Object grab distance shortened and object follows crosshair more quickly
Running into an object with the player now moves the object
The cursor now locks to the screen upon game entry and unlocks with escape
Object picks up from center of screen (crosshair) rather than from the mouse
Modified the light in the level
Added a tree to play with the tree generator
Merge pull request #33 from lazrcat0/GrabTweaks

Changes to pickup system + some tweaks