Added Profile78 v4.5 portable class library

- SystemClock.cs changed to Task.Delay via IFDEFs on PORTABLE
- BrokenCircuitException on PORTABLE is not Serializable.
changed namespace and assemblyname to Polly

Was "Polly.PCL" now "Polly" which is the existing convention.
corrected Thread.Sleep replacement

https://stackoverflow.com/questions/12641223/thread-sleep-replacement-in-net-for-windows-store
https://github.com/michael-wolfenden/Polly/pull/4#issuecomment-37346084
Merge pull request #4 from ghuntley/pcl

Added Profile78 v4.5 portable class library