Add example using libmagic for identifying files

Wrap libmagic cookie and function calls in a FileMagicService class.
Handle cookie opening and closing in constructor/desctructor, and
provide methods taking filename and calling magic_file to return

- Textual description of file type
- Raw MIME type
- MIME encoding
- All matches (textual) found by magic for the file

TODO : Error handling and possible use of cURL for remote file type
detection.
Add notes on the libmagic example

Note problems/ideas for reading data for the pipeline.