add second player embedded player to index.html test page
ignore all dotfiles, excluding special ones
add moderator script for embedded players
improve interaction for embedded players

Embedded players send 'play', 'pause' and 'stop' messages to opener window.
When an embedded player frame receives the 'pause' message they pause all players present.
Add some comments to clarify some decisions.
enhance webplayer embedding test page
use native event handling in moderator
refactor webplayer function pollHeight

* rename variable neuHeight to newHeight
* remove unnecessary log output when newHeight is null
* add second parameter to requestAnimationFrame call
restructured and improved webplayer moderator

* register `messageHandler` only once
* declare iframe dimension boundaries and defaults explicitly at the
beginning
* moved function `handleMessage` to outer scope of jQuery extension
(enclosing immediate function)
* discard message if no action is included in `handleMessage`
* function `pausePlayersExceptOne` sends pause command only if the
embedded player is currently playing (status is `1`)
* add docblocks to functions
* add function `getDimensions` that sanitizes the given value according
to min, max and default value
comment out debug statement in podlove-web-player