Got melody search based on Ngram and string distance working functionally.

 - Slimmed search to two steps, ngram identification and then similarity rating.
   Removed intermediate take-top similarity rating and related stuff.
 - Stripping of ngram occurrence intervals that are no-hopers.
 - Basic weighting on effective matched length multiplied by primacy within tune.
 - Consider each ngram occurrence interval on its own (i.e. many occurrences per tune) then pick best
   per tune rather than glom all occurrences together (recipe for combintorial explosion in the similarity).
 - Remove triangular area weighting equation, this one seems good enough.

 - Added histogram similarity, but not using it in the end. It'll come in useful later.

 - Remove goroutines and channels, it only cluttered and didn't make a massive improvement.
 - Tidyup of dead code