Add support for file naming patterns

[kward]

Patterns:

• Use @ for templating delimiters.
• Have some built-in defaults, but allow custom patterns from the command-line.

Variables:

• name
• track_no
• session_no
• extension

[kward]

Three initial patterns could be:

• by_session "@session_no@ @track_no@ @name@.@extension@"
• by_name "@name@ @session@.@extension@"
• by_track "@track_no@ @name@ @session_no@.@extension@"

[kward]

Hard coded support for Pro Tools (with auto detection for Pro Tools and Waves) added in 9e3d11e.