Document all the options and implied behaviors

[hartman]

I'm trying to figure out how it all works, but some of it is really badly documented, documented in locations that are no longer considered to be 'canonical', documented for the old version, or not documented at all.

For controlBar, i figured out:

• children, an array. determines 'presence in the dom and order'. can be used to override the default of:

[
    "playToggle",
    "volumeMenuButton",
    "currentTimeDisplay",
    "timeDivider",
    "durationDisplay",
    "progressControl",
    "remainingTimeDisplay",
    "customControlSpacer",
    "playbackRateMenuButton",
    "chaptersButton",
    "subtitlesButton",
    "captionsButton",
    "fullscreenToggle"
]

• the skin determines default visibility of controls.
• some of the controls are present but conditionally hidden (ie. chapters, captions etc)
• a hidden control has the vjs-hidden class, which can be switched with the .show() and the .hide() methods of the control.
• apparently currentTimeDisplay, timeDivider and durationDisplay are the only default present children that do not 'appear' to listen .show() and .hide(), as they by default are hidden by the skin.
• there are 'options', but no one really knows all the available options and their names :)

[gkatsev]

Fwiw, I updated the components.md doc in the doc/guides directly to have the latest version of components on the control bar/player.