Enable Number Scrubber and Color Picker

[jeresig]

This will have to work in two parts:

• We'll have to update the PJS definitions to include some indicator that a number (or color) is desired for a particular input.
• The Live Editor StructuredBlockEditor will need to bind to those hooks for the numbers/colors.
• The pickers will need to communicate their results back to the PJS nodes (possibly using a DOM event).

[pamelafox]

I realized there's a bit of a difference between the number picker and the color picker experience. The number picker should pop up per input field, but the color picker needs to pop up per the entire block of parameters. Something that needs to be dealt with on the event listening level. Not sure how it will feel from UI perspective. @lemiant @jbrennan

[jeresig]

This has landed!