Add Klawr.ClrHost.Managed C# project
Startup the CLR host when the ScriptPlugin module is started up
Update the IKlawrAppDomainManager interface
Set the target framework for Klawr.ClrHost.Interfaces project to 4.5

Not sure why it was set on 4.0 before, since Klawr.ClrHost.Managed is
set to 4.5.