Fixed bug in refactored AnnotTrack.executeOperation for handling errors
Added support for 'N' when creating genomic alterations.
added test for correct parsing of simple GVF by flatfile-to-json.pl (test passes with existing code)
added code and tests for support of VCFs in flatfile-to-json.pl - SNVs work, but not inels (yet)
added some random test fixtures
Merge commit '5b433'

Conflicts:
	plugins/WebApollo/js/View/Track/SequenceTrack.js
	tests/perl_tests/flatfile-to-json.pl.t
replace custom arrowheads with copies of the arrowheads from JBrowse core
Merge remote-tracking branch 'origin/master' into just_webapollo_plugin