Refactor copydb_init_specs to use a CopyDBOptions struct. (#229)

Rather than having to add so many parameters just re-use the options struct
as a parameter there.

We still want to have a separate command line option structure rather than
use the internal tracking CopyDataSpec structure at command line parsing
time, but we can still simplify the code a good deal.

This allows easier adding of new command line options in the future.