First draft color picker

Summary: This implements a first draft version of colorpicker for structured blocks. I don't like how it works, but it works :P. We can probably use it as a stopgap for a while

Test Plan:
View demo
- Add fill
- Change fill color
- reload see that colors are still right

Reviewers: john, pamela

Subscribers: #cs

Differential Revision: http://phabricator.khanacademy.org/D14620
Re-work colorPicker to use new Structured blocks color model.
Merge with master.
Update structured-blocks.
Move tooltipEngine stub.
Add in support for the number scrubber.
Update structured-blocks.
Merge branch 'arcpatch-D14620'