Allow dependencies custom path

[tormento]

What about having a preferences file inside DeeZy directory to have custom dee and ffmpeg paths?

[jessielw]

In it's current state it can detect both DEE and FFMPEG on the system PATH, it can check for them beside the executable in the apps directory, and it also supports [--ffmpeg FFMPEG] [--dee DEE] as switches to define custom paths at runtime.

Knowing all of this information would you still like an optional configuration file added?

[tormento]

The path can be very long and therefore the commandline cumbersome and hard to remember.

A config file would be nice, such as also default parameters per certain channels number, DRC, etc… so we can launch DeeZy with a lean and clean command line, such as DeeZy -i input.whatever output.whatever.

[jessielw]

I'll look into implementing this soonish