Add constrsints layout copied from enable branch
Add example creating subplots with constraints-container.

The layout is a bit busted, but that's not too important
Remove requirement to set component id
Fix subplots layout
Remove original constraints example
Add constraints tests
Rename for clarity
Merge branch 'master' into exp/constraits-layout-merge-master

Conflicts:
	deli/canvas.py
	deli/core/component.py
	deli/plot_component.py
Merge branch 'master' into feature/constraints-layout
Add default layout-constraints