Replace 'shntools' with 'flac' for splitting

[ NEW ]  Replaced using 'shnsplit' ('shntools') with 'flac' when splitting
         music images

[ NEW ]  Added '__decode_file' function since we now need to operate on
         either a FLAC file or a WAV file (used by 'flac' when
         splitting).
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[ ENHANCEMENT ]  Removed dependencies on 'shntools', 'ffmpeg', and
                 'ffprobe'

[ ENHANCEMENT ]  Replaced C for-loops with range expressions

[ ENHANCEMENT ]  As a result to not using 'shntools', we can now remove
                 the CUE period function (hack)

[ ENHANCEMENT ]  '__cue_resolution' is now '__cue_milliseconds', since we
                 now convert _ALL_ CUE's from frames/sec to milliseconds
                 in order for 'flac' to understand the split points

[ ENHANCEMENT ]  Simplify the operations array by removing the need to
                 store the beginning file count (used by 'shnsplit')

[ ENHANCEMENT ]  The '__tag_files' function is now simplified since we
                 no longer need any 'shntool' workarounds
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[ FIXED ]  Various code cleanup