Load static patterns first, then localStorage ones.
Display scrollbar on preset tab.

This is a regression from moving to using "tabs" directive. Before that
change, the tabs had the .tabs class, but it was removed. This change
adds it as part of the directive.
Clean up CSS a bit.

* remove range/enum/color classes
* value -> slider-value, buttonset-value, colorstop-value
* remove unnecessary #presetMenu from some rules
Fix off-by-one bug when saving screenshots.
Screenshot command takes a file format parameter.

Only JPEG/PNG supported.
Move color processing to its own file/service.
Change license from Chromium to Apache