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-generated code (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.