Part 16: PluginVersion Changes

+Improving PluginVersion.cs :
+modified invocations of versionated members on PropellerCPU.cs and
Emulator.cs.
+Added experimental new Attribute ParamVersion() class to decorate
params of versionated methods.
+added experimental method InvokeVersionatedMethod() to call from
Emulator class (ex. PresentChip versionated member).
+added attribute IsUserPlugin() to PluginBase class to distinguish
between  User or System plugins.
+added overriding property IsUserPlugin to Cogview, LogicView & SpinView
classes derived from PluginBase.