Fix for issue 836.
When plugin initialization fails properly reject the deferred queue and
propagate (and handle) undefined as evaluator return value.
Fixed plugin loading for other languages as well.
Merge pull request #839 from twosigma/ildipo/issue-836

Ildipo/issue 836
Merge remote-tracking branch 'origin/master' into ildipo/issue-840

Conflicts:
	core/src/main/web/app/mainapp/mainapp.js