Make WebKit+Safari Flash fs toggle API-safe (#586)

Instead of calling high-level play() in the fullscreen module re-write
flashvars if video url has changed in the flash module. Thanks
@forrest79 for inspiration.

This
- takes care of url changes in playlists and via the api, e.g. load()
- allows to simplify the fsResume hack in the fullscreen module
flowplayer/flowplayer#586: always resume live streams

Getting back to paused state immediately after reconnect makes the
player get stuck - even with version 5.4.3 of flowplayer.swf where
resuming of live stream works (flowplayer/flowplayer#570).
Merge pull request #611 from blacktrash/bug/586

Make WebKit+Safari Flash fs toggle API-safe (#586)