Support for Non-CCK Fields - apachesolr_custom_field_mappings()

Attached it is a first pass at adding support fro non-cck field data to (a) the indexing process and (b) facet block generation. My test use case was to index some field data from the biblio module, which stores citation data in its own table structure. The hook implementation looks like this:

/*
* Implementation of hook_apachesolr_custom_field_mappings()
*/
function biblio_apachesolr_custom_field_mappings() {
  $mappings = array();
  $mappings['biblio_secondary_title'] = array(
    'index_type'    => 'string',
    'field_name'    => 'biblio_secondary_title',
    'label'         => t('Biblio Publisher'),
    'is_multiple'   => FALSE,
    'facet'         => TRUE
    );
  $mappings['biblio_contributors'] = array(
    'index_type'    => 'string',
    'field_name'    => 'biblio_contributors',
    'label'         => t('Biblio Contributors'),
    'is_multiple'   => TRUE,
    'callback'      => '_biblio_index_contributors',
    'facet'         => TRUE
    );

  return $mappings;
}

//helper callback - cram all types of authors into one field
function _biblio_index_contributors($node, $fieldname) {
  $contrib = biblio_parse_contributors($node->biblio_contributors);
  foreach ($node->biblio_contributors[1] as $contributor) {
    $contributors[] = sprintf('%s, %s %s', $contributor['lastname'], $contributor['firstname'], $contributor['initials']);
  }
  return $contributors;
}

A couple of things to note:

1. In apachesolr_search.module, $index_key needed a $delta concatenated to it for CCK/custom fields w/in apachesolr_facet_block(), so I added that
2. I implemented temporary fix for granular field mappings to test some non-option widget CCK fields (see 271753)