SDK / exoplayer

Github issue: #375

This package will house all extractors, which will be unified
to implement a single Extractor interface.

The limit on the ts packet buffer can be reduced during processing
if it's discovered to have padding. Hence we need to reset it back
to the ts packet size before processing each packet.

- Atom related stuff in Mp4Util is moved to Atom.
- Remainder of Mp4Util is renamed to H264Util.

- Keys should not expire during normal playbacks of correctly configured content.
- Attempting to refresh on expiration causes a race condition, that may result
  in either failure or brief re-buffer, for the 30s license test video.
- This change provides deterministic behavior, which is to always fail.

Some servers, probably edge cache machines that exclusively serve
chunked media, don't support partial requests. Which is kind of
vaguely reasonable for that particular case. This change modifies
DefaultHttpDataSource to correctly handle this case, by manually
skipping data up to the requested position (and making sure not to
read more data than the requested length).

better handling of input format change for non-adaptive codecs

The regex included quotation marks like X="YES", but the manifests
don't actually contain them, for examples X=YES.

- Have extractors read from an ExtractorInput. Benefits of this are
  (a) The ability to do a "full" read or skip of a specified number
  of bytes, (b) The ability to do multiple reads in your extractor's
  read method. The ExtractorInput will throw an InterruptedException
  if the read has been canceled.

- Provides the extractor with the ability to query the absolute
  position of the data being read in the stream. This is needed for
  things like parsing a segment index in fragmented mp4, where the
  position of the end of the box in the stream is required because
  the index offsets are all specified relative to that position.