Feature: Allow audio_norm.sh to detect sample rate and bitrate/bitdepth of the input file's audio stream

[iamdamosuzuki]

Right now audio_norm.sh only maintains the file's original codec, not the more important format details.

[eddycolloton]

Added a line to excerpt the audio bit rate from mediainfo in PR #16 but it's a bit hacky, needed to clean up grep output so it doesn't grab video bit rate or overall bit rate.
The line to excerpt the sampling rate from mediainfo in PR #17 is cleaner since it's the only "sampling rate" mediainfo field