SDK / exoplayer

- 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.

- Move to builder naming.
- Propagate formats to the TrackOutput instances, rather than having
  them be read through the Extractor. There was actually some weird
  indexing going on here before (which happened to work, but wasn't
  well defined).

Fix AES decryption of HLS streams.

As per http://tools.ietf.org/html/draft-pantos-http-live-streaming-04#section-5.2,
the initializaton vector (IV) of the AES decryption algorithm should be set to:
- the IV attribute value if present,
- the sequence number otherwise.

Currently, the IV is set once and use over all next media sequences
where the IV attribute is not set. The fix is to use the provided IV if
given or use the current media sequence number.

- It's probably easiest to think of this as a standalone HLS change, which is splitting out the "loading" and "consuming" sides of HlsExtractor and a good structural change in its own right. To do this, HlsExtractorWrapper becomes a final class implementing the consuming side. HlsExtractor becomes an interface defining the loading side.

- The bigger picture is that, hopefully, HlsExtractor will become a lightweight extractor interface that can be used throughout the library. Because it doesn't need to implement the consuming side, we'll save on having to re-implement the consuming side for every extractor (we'll probably need one consuming side implementation for HLS/DASH/SmoothStreaming, and a second one for everything else, both of which will use SampleQueue). It's expected that the HlsExtractor interface will need to change to accommodate all use cases.

- The next step in unification will be to try and have FragmentedMp4Extractor implement HlsExtractor (which will need renaming). Once this is done, I'll try and move the chunk package over to use the HlsExtractor interface.

- This is a step toward hopefully converging HLS and CHUNK packages.
- Add support for encrypted samples.
- Add support for appending from a DataSource.

- The fmp4 extractor was reading from sampleEncryptionData even
  for not-encrypted samples, which I'm pretty sure isn't right.
  Fixed this. For all encrypted content I've seen, this change
  will be a no-op because isEncrypted is always true if there's
  an encryptionBox present.
- Made webm extractor only set cryptoInfo if isEncrypted is true.
- Align variable naming in the two extractors, for clarity.

- Rather than returning a map, return a DrmInitData object,
  with mapped and non-mapped implementations.
- Include a suitable mimeType to pass to the MediaDrm. Previously
  we were incorrectly passing the mimeType of the samples,
  where-as MediaDrm expects the container mimeType. Note that
  it doesn't matter whether the mimeType starts with "video" or
  "audio", hence using video mimeTypes everywhere.

Not yet used by anything.

Issue: #151

- Correctly handle bandwidth NO_ESTIMATE case.
- Don't consider switching without a previous chunk.

Set the duration on the MediaFormat instead.

Issue: #327