Teach the staff client volume copy creator to respect OU call number preferences

Teach the staff client volume copy creator to respect OU call number preferences

To teach the "Add volumes" dialog in the staff client how to show the correct
set of call numbers based on the workstation OU's default classification
scheme, this commit:

  * Adds a column "field" to the asset.call_number_class table that specifies
    the list of tag/subfield combinations to search for a candidate call number
    for a given classification scheme
  * Adds a new OU setting, 'cat.default_classification_scheme', that points
    to the asset.call_number_class ID
  * Extends the open-ils.cat.biblio.record.marc_cn.retrieve method to support
    a second argument, identifying the classification scheme for the call
    number extraction
  * Fixes the IDL for asset.call_number_class to include the ID as an explicit
    field
  * Makes the "Add volumes" dialog look up the 'cat.default_classification_scheme'
    setting for the workstation OU and apply that to the call to the
    open-ils.cat.biblio.record.marc_cn.retrieve method

TODO:
  * Provide a means of switching the classification scheme for the current volume,
    repopulating the call number selector widget
  * Save the chosen scheme as part of the acn object

git-svn-id: svn://svn.open-ils.org/ILS/trunk@17141 dcc99617-32d9-48b4-a31d-7c20da2025e4