config.disableDesktopSharing - when set to false will disable desktop
sharing

interfaceConfig.DESKTOP_SHARING_BUTTON_DISABLED_TOOLTIP - when value is
assigned, will not hide the desktop sharing button completely, but show
as disabled with this value used as the tooltip text.

Rewrite the non-React RingOverlay into the React Component CallOverlay
in a way which makes it easier to port to React Native.

- Add a class to the body when in vertical filmstrip mode
- Override styles as necessary to support the mode
- Add an option to make tooltips display from the left
- Move the HD Label to the bottom left
- Move the remote video menu to the bottom left, move the mute
  icons to the bottom right
- Scale the local video's height and width to fit the filmstrip

Audio only mode will be toggleable only from the VideoStatusLabel,
so remove AudioOnlyButton from the toolbar and delete the component
itself. As a result of the button being removed, a truthy check in
VideoStatusLabel was also removed to ensure it will display as it
is now the only way to toggle audio only mode. Also set the cursor
on VideoStatusLabel to always be default, so it can never show the
text cursor.

Audio only mode can be used to save bandwidth. In this mode local video is muted
and last N is set to 0, thus disabling all remote video.

When this mode is enabled avatars are shown.

Disable the button, till we need it, UI is fixed and it is tested that everything works from jitsi-meet, through lib-jitsi-meet and through jigasi.

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

Merge pull request #760 from aaronkvanmeerten/master

update whitespace in toolbar buttons array to allow value to be more easily overridden