Add support for AIFF

- add support for
  - TagLib::RIFF::File abstract class
  - TagLib::RIFF::AIFF::File class
  - TagLib::RIFF::AIFF::Properties class

- added swig code for RIFF and AIFF.
- added swig wrappers, generated against TagLib 1.7.
- added test code for reading/writing tags to/from AIFF files, including cover-arts.
- added an AIFF-encoded audio file with ID3v2 tags for tests.
- added documentation.
As this is new API, we'll release 0.7.0, see http://semver.org/