Add common properties file to test framework

[pakrym]

Improving 2 things:

1. Groups shared files into a directory:

Before:

After:

2. Avoiding everyone having to add None Update="SessionRecords\**\*.json" into every test project.

[jsquire]

Would be very nice to break the shared areas for the framework into a project that could be referenced but not included in the solution for a client library in the same manner as Core.

That would avoid the appearance that the client library owns the files and the expectation that changes are scoped to only that library and, therefore, safe.

[pakrym]

I would be happy to extract the test framework into a project/package but there are some related infrastructure challenges we don't want to address right now.