[0.6.169] use attr for buffering criteria

[0.6.169] use attr for buffering criteria

- Use attr for prebuffer_ms and rebuffer_ms value
  to seperate between platform default and user requirement.
- In case of TS content, update duration
  via gstreamer query when user ask the duration value
  TS duration is getting accurate over time.
- Add setting about low-watermark property to buffer
  based on the high-watermark.
  If not, according to the user request, the high-watermark
  can be similar with low-watermark which was fixed to 10% of buffer size.

Change-Id: I23f977280479d7264449eea8d947a0997781a9d2