Added support for getting app sessions by User [ListCurrentAppSessions()...

I tried compiling the solution, but could only do so after adding a reference to TerminalVelocity manually - don't know how to fix the nuget package.  Our R# automatically adds a copyright date, which can be ignored.

I think this is useful (I have tried the API and it seems to work fine)
I believe your request object should just inherit from the existing
AbstractResourceListRequest, was there a reason to not use that?