Use subscribers to detect state change and emit those
out to other participants. Use middleware to register
the command listener.

showControls instead of showControns

This PR takes The Bulldozer Approach (R): removes the old toolbox and lots of
associated code, though not all of it. Subsequent cleanups will follow.

- Modify Etherpad and SharedVideo so their resizing takes into account
  the width of the filmstrip in vertical filmstrip mode.
- Modify Filmstrip's getFilmstripWidth to account for when the filmstrip
  is hidden.
- modify VideoContainer so in vertical filmstrip mode it centers the
  shared desktop stream in the middle of the available space not taken
  by filmstrip.
- Also allow clickthrough on the secondary toolbar itself while still
  allowing clicks on the toolbar's buttons. This allows clicks on
  shared videos to go through.

Prepares for the latest eslint & flow-related npm packages which cause
these errors.

We seemed to be using the names "film strip" and "filmstrip" (and,
consequently, their source code-conscious forms such as film-strip,
FilmStrip, etc.) In order to comply with our coding style which requires
a consistent one name for a given abstraction, choose one name and
rename the uses of the other name.

Wikipedia has a definition of a "filmstrip", I couldn't find a "film
strip". I guess our abstraction can be seen as what's described there.
When I google "film strip", I get results about "filmstrip" at the top.
That's why I chose "filmstrip".

Certain uses of "film strip" such as interfaceConfig.filmStripOnly and
in the external API I left untouched in an attempt to preserve
compatibility.

I wasn't sure whether CSS was tangled in compatibility so I made a
choice and renamed there was well.

Enable ESLint on jitsi-meet with the same configuration and the same
goals as in lib-jitsi-meet.

This reverts commit 93648f361b.