Made changes to the client to use HttpClient

- excluded SL and WP8 from code analysis for the time being
#1908
Made changes as per code review feedback

#1908
Modified SignalRError

#1908
editing samples
Excluded SSE for SL
Removed redundant platform specific code

#1908
Removed unnecessary compilation symbols

#1908
Removed SL and WP8 from code analysis

#1908