Synced the Options Screen and Pause Menu Volume Sliders

- The volume Sliders on both the Options Screen and the Pause Menu will now be updated if either Slider is updated. Before, the Pause Menu sliders would not be updated to reflect the change in volume on the Options Screen, and vice versa
- Increased the volume range from 0 - 10 to 0 - 20. This gives the player more volume options for both music and sound. Changed all code appropriately
Created Larger Shop Icons

-Created ShopItems for buying and upgrading Slowers and Archers
-Replaced the smaller icons with the bigger ones
Create a larger Invincibility icon
Made Consumables Show Up Correctly on the HUD

- Consumables were showing up too small on the HUD. Fixed this by editing the GridViewStyle and GridViewItemStyle XAML Styles in App.xaml to reduce the margins and padding within the control templates that were making the items too small
- Made consumables show up on the HUD when the user continues a saved game
- Removed consumables from the HUD when the user starts a new game
- Created the AddConsumablesToHUD and RemoveConsumablesFromHUD methods in Shop.cs
- Added padding to the HUD_ConsumablesList on the HUD so that consumables do not show up as large as the gold image. This was done to prevent potential confusion
- Found three music tracks that might be able to be used
Better balanced the game

-Made enemies able to spawn with invincibility starting at Level 15
  -The duration of the invincibility starts out at 1900 ms and decreases by 50 ms each level due to increased enemy speed

-Made FlyingGoblins attack the fastest and ArmoredGoblins attack slightly slower
-Adjusted damage values; slower attacking enemies hit harder while faster ones do less damage
-Created a large Invincibility Icon
-Added sounds for:
  -Swinging your weapon
  -Goblin dying
  -Purchasing an item

-All weapons use the same swinging sound
Merge branch 'BalancingTweaks' into ConsumableItemsFix
Merge branch 'ConsumableItemsFix'