Remove XAxis and YAxis.

References have been updated to Abstract.Axis or Axis.Numeric where appropriate.
Merge branch 'master' into remove-X-Y-Axis

Conflicts:
	test/components/axisTests.ts
	test/testReference.ts
	test/tests.js
Merge pull request #664 from palantir/remove-X-Y-Axis

Remove XAxis and YAxis.