[FA]{issue} I67 - enemy flashlight behaviour

#67
-added a method to entity to switch to a specific item
-replaced array item array with item maparray
-enemy switches to flashlight at start of a level if he is in the
darkness at that point
[FA]{issue} I73 - camera

#73
-added camera texture
-added light to camera
-minor camera changes (position in constructor)
[FA]{issue} #74 - entity drop and pickup items

Closes #74
-Entity can now drop and pickup items
-Added keys and buttons to player
-Added Item Manager: holds all items currently not held by an entity
-draws all items
-Buttons only active when player has an item selected / there is an item
in reach that can be picked up etc.