added boundary ctxs & plug to core
t_context_typing and t_context
Merge branch 'master' of https://github.com/phillipm/cps-from-stlc-to-sysf

Conflicts:
	src/Core_Definitions.v
Merge branch 'master' of https://github.com/phillipm/cps-from-stlc-to-sysf