Change long polling request to use same URL and POST instead of GET

- Update client protocol
- This change is intended to avoid a memory leak in IE/Chrome

#2953
Stop using the PreserveCultureAwaiter in MessageBroker and Subscription
Remove resource string in trace message

#2920
UntilServerDoUsApart - implementing logic for starting WebSocket transport on WindowsPhone 8.1.
BetterPath - updating path to MSBuild to use v12 required to build Windows Store projects.
Backtalk - implementing Send in the Store WebSocket transport
ThisPesteringClient - adding support for reconnect

Client will now reconnect if the underlying WebSocket gets closed unless a reconnect timeout is exceeded or the operation has been cancelled.
ThinkYouReSoCleverButNowYouMustSever - WPA81 WebSocket transport disconnect
AccidentalRefactoring - removing an unneeded public method

One of the methods was made public for testing purposes but since we now have InternalsVisibleTo it can be removed.