Better app streaming and StyleCop fixes (#283)

* Refactored use of async. No tight while-loops but instead using await and continue on background threads.

* Remove use of .Wait() to avoid potential deadlocks. increase use of ConfigureAwait, and remove await where not needed

* Simplified async code. Instead of forwarding to tasks and have to switch to ui thread, it's easier to just await and continue on the same thread here.

* First stab at using a custom http multipart content to avoid large memory consumption when installing large files.

* Changed implementation to Explicit

* Use proper separation between attachments

* Resolve header ordering issue in .NET, and force non-quoted boundary

* Boundary fixes.

* Update last merge

* StyleCop fixups

* Added streaming improvements to xbox's loose deploy as well