Initial Shop Window Created

ShopScene class created with buttons to switch between Trains and
Obstacles.
Buttons Added

Resources and Next Go buttons added.
More Buttons Added

Shop, Resources and Goals buttons added on toolbar.
Efficiency Improvements & Toolbar assets added

Creating window background image in much less code. Assets for toolbar
for player indicator, fuel and money added.
Label Class Added

Label Class created and labels added to the shop window.
Merge pull request #2 from JASApplications/Shop-Window

Initial Shop Window Created