add API to toggle
- URL cache flush in live mode
- start the playback from lowest level

related to https://github.com/mangui/HLSprovider/issues/69
related to https://github.com/mangui/HLSprovider/issues/90
add config parameters for HLSProvider/jwplayer5-6 and ChromelessPlayer

jwplayer: allow configuration when setting up the player :

jwplayer("player").setup({
...
hls_debug : false,
hls_debug2 : false,
hls_minbufferlength : 3,
hls_maxbufferlength : 60,
hls_startfromlowestlevel : true,
hls_live_flushurlcache : false,
hls_live_seekdurationthreshold : 60,

fix https://github.com/mangui/HLSprovider/issues/69
related to https://github.com/mangui/HLSprovider/issues/90