Not accepting vertical-right/vertical-left as orientation for Label.

Close #1108.
Merge branch 'develop' into label.orient_consistency

Conflicts:
	plottable-dev.d.ts
	plottable.d.ts
	plottable.js
	test/tests.js
Merge pull request #1110 from palantir/label.orient_consistency

Not accepting vertical-right/vertical-left as orientation for Label.