Overhaul the marc2sre.pl script for importing MFHD records

Overhaul the marc2sre.pl script for importing MFHD records

Add --bibfield / --bibsubfield options to support retrieving the
bib record ID by searching the specified field/subfield for the
identifier, instead of assuming that the identifier =
biblio.record_entry.id. Avoiding the lookup will be much faster, but
some sites want to start clean with their bibliographic record IDs,
so this supports them.

Remove the need for passing in the owning user's password and simply do
a lookup by username in the actor.usr table. This is a bit more secure
as the password isn't exposed on the command line and you can easily set
someone else as the owner of the records without having to know their
password.

Add significant internal help via Pod::Usage.

git-svn-id: svn://svn.open-ils.org/ILS/branches/rel_2_1@19990 dcc99617-32d9-48b4-a31d-7c20da2025e4