Avoid using updateContentScripts() as it suffers from an unexpected
behavior, causing injected content scripts to lose proper order
at injection time. The order in which content scripts are injected
is key for uBOL content scripts. Potential out of order injection
was causing cosmetic filtering to be broken.
Use actual storage API to persist data across service worker
wake-ups and browser launches. uBOL was trying to avoid using
storage API, at the cost of somewhat hacky code (using DNR API
to persist settings).
Make use of session storage if available, to speed up
initialization of waking up the service worker (which at this
point is necessary to properly implement cosmetic filtering).
`uDom` is old and crusty and `dom` is meant as replacement. The
goal of `dom` is to be simpler and mainly just convenience
methods for handling the DOM with vanilla JS -- this is not a
framework.
Additionally, removed keyboard shortcuts pane which was useful
only on very old versions of Firefox.
