Merge pull request #9 from alexrp/master

A few changes to make using Mono.Debugging more practical
Sprinkle around some magic readonly fairy dust
Fixed DebuggerSession.ResolveExpression() to not require a type resolver
[Mono.Debugger.Soft] synced up with Mono
[Mono.Debugging.Soft] Filter DebuggerStepThrough as well
[Mono.Debugging] Added some sanity checking on some public APIs
Fixed the build
Pass setpgid=y to the soft debugger agent.