Add getter/setter for Netstream.bufferTime to control buffering

The video-js-swf doesn't have the interface to get/set Netstream.bufferTime and have set bufferTime=1(second) internally. It's almost working if network bandwidth is enough for streaming. However, handling the bufferTime is useful for narrow bandwidth.

Adobe documents describes how to handle the bufferTime dynamically.
http://help.adobe.com/en_US/flashmediaserver/devguide/WS5b3ccc516d4fbf351e63e3d11a0773d56e-7feaDev.html#WS82FD33FA-43D8-4f7a-BEAE-E3950CB694A1Dev
> you have an escalating bufferTime value which is triggered by the initial bufferTime being filled (via the Buffer.FULL event trigger). 

Yes, exactly.

> Problem is, Buffer.full triggers irregularly based on network conditions.

Certainly. I monitored when Buffer.full happens on unstable network, and then confirmed 2 pattern.

 1. Buffer.full happens after Buffer.empty
 2. Buffer.full doesn't happen when bufferLength value > bufferTime without Buffer.empty

So, I thought escalating bufferTime is efficient since Buffer.full event is irregularly.

As you know, it's better to configure bufferTime as a parameter to video.js and I hope it. To do so, I thought video-js-swf should have the interface to handle bufferTime. HTML tech doesn't have bufferTime from flash player since it's from progressive download, no need to control buffer. So we don't need to consider bufferTime for HTML tech.