and related tools.

with larger vectors and high bit sizes than the current LSH tool.
These are the new hash_similar_angles_xxx objects.

avoid duplicate code and generally cleaned things up a little.

a little nicer.

coded.  I also increased the default threshold to a more reasonable value.  The previous
value hardly excluded any points and gave a slightly worse average precision on a standard
test dataset.

based on the input pixel type rather than always using long.

on C++11 compilers.