Split the WindowsSDK locations out of VisualStudioInstall
Removed some unused stuff from ToolChainRegistry

- availableToolChains is not required
- defaultToolChain is not required
Rename variable for clarity
Minor spec updates
Added integration test for executable using mix of libraries

- Combined shared + static library
- Combined library from same project + library from another project
Moved open issues for story so that this story can be considered complete