A MonoTouch port

This is a MonoTouch port of the main Common.Logging solution.  I was able to reuse most of the code, taking out references to System.Configuration, and System.Diagnostics.Trace in places.

The MonoTouch logger only supports the ConsoleOutLogger, and doesn't support app.config files.  Instead it supports a plist file (default is Settings.bundle/Common.Logging.plist).

For the unit tests, I removed System.Configuration and Trace logging as well.  All tests pass.

I wasn't sure where to put it in the source tree, so I followed similar patterns as the ServiceStack project.