SI-7995 completion imported vars and vals

Imported member vals and vars were always marked inaccessible, even
if referencing them at the location of the completion is valid in code.
The accessible flag is now set accordingly to the accessibility of the getter.
SI-8019 Make Publisher check PartialFunction is defined for Event

Reactions are PartialFunctions, so if events come through
indiscriminately that the listener is not defined for, errors occur. Eg:

--
Exception in thread "AWT-EventQueue-0" scala.MatchError: FocusGained(scala.swing wrapper scala.swing.TextField
--

A Coursera thread with people affected by this issue:

https://class.coursera.org/reactive-001/forum/thread?thread_id=1315
Merge pull request #3244 from rtyley/si-8019-swing-publisher-check-pf-defined

SI-8019 Make Publisher check PartialFunction is defined for Event
Merge pull request #3222 from skyluc/issue/completion-import-vals-210-7995

SI-7995 completion imported vars and vals