rework event api
remove debug code.
improve docs.
move 'observable' module from conductance to sjs stdlib
Merge branch 'master' into events-refactor

Conflicts:
	modules/sjs-lib-index.json
docs
surface::Enabled() should set attribute, not class
polymorphic event::wait
update std.sjs
Merge branch 'master' into events-refactor
minor code simplification