made sure that any Instance could find the policies of the root PluginGraph
added a convenience method to Policies for selecting a constructor
checkpoint: got *most* of the cutover from the old IInstanceBuilder/Argument internals to BuildPlan w/ ConcreteBuild
checkpoint: fixed a UT with optional setter injection after the BuildPlan switchover
checkpoint:  introduced a generic InstanceDependencySource that just delegates, still problematic though
checkpoint: changed internal signatures of build***() methods in Instance to use IBuildSession instead of concrete BuildSession
completely switched over to the new BuildPlan concept for constructor instances (Woohoo!)
integrated the BuildUpPlan into the Container usage
moved the BuildUp tests on the old InstanceBuilder to using the new BuildUpPlan.  Closes GH-126
ripped out the old InstanceBuilder and IArguments classes
changed the ctor of EnumerableInstance so that it does not have to know the property type upfront
thinning down IConfiguredInstance, removed SetCollection
thinning down ConfiguredInstance, removed GetProperty
removing IConfiguredInstance.AddProperty() to continue thinning down IConfiguredInstance
removing SetChild from IConfiguredInstance to continue thinning it out
removed the GEt() and SetValue() methods on IConfiguredInstance to continue thinning down IConfiguredInstance
removed old HasProperty method off of IConfiguredInstance
removed more old implementation in ConfiguredInstance before killing off Plugin once and for all
removed IStructuredInstance
removed some dead code in ConstructorInstance