Remove special "hash" column type, just use binary.

This causes problems with column builder (because hash is already
defined method). In addition the vast majority of uses of binary
columns are going to be for hashes, so just set the appropriate
defaults which can be overridden if necessary.
Make unique actually generate a unique index.
Fix query spec so that it works on latest Sequel

Sequel has started adding ESCAPE after LIKE phrases since 3.45
Version bumpt to 0.4.3