add video options(width,height,scale,limit)

[necnecnec]

Add some videotrack options to fix bug or add new feature
--width/height fix (width/height in context.drawImage is the analysed video width/height,may need specify) **you may get width/height by bind("playing",function(){});
--scale (sometime video quality is too high may need scale to reduce,or it will use too much rescoures)
--limit (like scale,sometime we don't need two high fps,use this to reduce)

I have tested these features。if you are interested，I can rewrite these。