Updates to Menu, Removal of Targeting and Reticle

* LoadMenu animation updated
* Selecting different Weapon buttons in Menu will correctly highlight
and change Player's weapon
* Removed calls to TargetButton and TargetReticle and their mechanics
* Removed Enemy's PlayerInRange variable (redundant due to EnemyInRange
* Removed Player's enemiesInRange variable (redundant since it is
identical to the size of the Player's EnemyList)

TODO:
* Simplified shooting mechanic (left-click on enemy to fire current
weapon)