Added a BuildCustomQueryString function to the TransportHelper

- Verified its functionality against the test project that was provided in #1556
- Need to add some tests to verify the functionality
#1556
Added a Functional test to verify the correctness of #1156

#1156
Added isNullOrEmpty check to transport helper instead of plain null check.

- Either result turns out to be a failed negotiate request.
Added unit tests to verify TransportHelper functions that are used via the negotiate

#1556
Addressed code review comments

- Added new test cases
- Updated appendCustomQueryString to be more flexible
- Removed enable cross domain from functional test
#1556