Fix auto scale domain on stacked plot.

It uses stacked logic in metadata.

Close #1340.
Merge branch 'metadata_stacking' into auto_scale_stack

Conflicts:
	plottable.d.ts
Add test.
Merge branch 'develop' into auto_scale_stack

Conflicts:
	plottable.js
	src/components/plots/abstractXYPlot.ts
	test/tests.js
Merge branch 'develop' into auto_scale_stack
Merge remote-tracking branch 'origin/metadata_stacking' into auto_scale_stack
Merge branch 'develop' into auto_scale_stack
Regenerate file.
Merge pull request #1413 from palantir/auto_scale_stack

Fix auto scale domain on stacked plot.