DDCN callnumber splitting with test.

DDCN callnumber splitting with test.

Similar to previous patch for LCCN splitting, this patch incorporates
changes to split_ddcn and supplies a test file for verifying proper
operation.  Note that the only previously documented example for intended
operation is included as one of the tests.

This regexps are created to be rather forgiving.  For example, the function
will not choke if two spaces were included where the "spec" (such as it is)
expects one.  Obviously this is because for CN splitting purposes, it doesn't
matter, we're not going to ever split in the middle of whitespace.

Signed-off-by: Galen Charlton <galen.charlton@liblime.com>