Refactor chrome/tab styling, re #7

Activate using:

  require("xulstyle").style(aWindow or getMostRecentWindow())

Adds "hotdish" class to tabbrowser-tabs.

stylesheetservices.js from:
  https://github.com/KWierso/rtse/blob/rtse-lite/lib/stylesheetservice.js
Merge branch 'master' of https://github.com/mozilla/hotdish