add configuration option to pass extra args to flac encode

[kevmitch]

Add an argument to the whipper cd rip comand that can be provided on the command line or in the whipper.cd.rip section of the config file.

It is retrieved inside the _ripIfNotRipped() private function, split into a list and passed down through to program/flac.py, which actually calls the flac binary.

Add debug logging to that function so the actual command shows up in the debug log.

Add a unittest to ensure that arguments passed to flac.encode() work as expected.

Tested ripping a disc with --extra-flac-encode-args="--best -e --no-padding" from both the command line and config file as well as with the default empty value.

Signed-off-by: Kevin Mitchell [email protected]