Added in an Animation system

-Added Animation.cs, which contains classes Animation and AnimFrame
-Added constant strings that represented directories to load Graphics, Sounds, and Music
-Created a folder titled "Graphics" in the Content folder and moved all relevent graphics there
-Put a test animation on display when you click to play the game
Created the Enemy class

-Started setting up enemies
Merge remote-tracking branch 'origin/AnimationSystem' into EnemySetup
Created More of the Enemy Class, and Got Enemy Movement Working

-Added an Animation to each Enemy
-Made a test enemy draw on screen and walk from one side of the screen to the other
-Made an ExitGame method in Game1.cs
-Made a StopSong method in SoundManager.cs
Merge branch 'EnemySetup' into PlayerSetup
Created the Player Class

-Set up the player and his castle
Cleaned up Players

-Removed some unneeded variables from the Player class
-Made all of a LevelObject's children die if the LevelObject dies
Created the Shop and ShopItem class

-The Shop contains many shop items
Added a basic AI system for enemies

-Added Action.cs
-Added a few properties and helpful methods, such as a missing Restart() method for Animation
Merge branch 'EnemyAIFlexibility' into ShopSetup
Merge branch 'ShopSetup'