centralize/register node facets blocks

Looks like a good start, but we need to think about whether we want to call the hook fmor apachesolr.module or apachesolr_search.module

I see a significant bug here:

+          foreach($facets['facets'] as $facet => $facet_value) {
+            if (!empty($facet_value)) {
               $params['facet.field'][] = $facet;

That assumes that the delta is the same as the facet field, which we know is not true. With this code, I thin kwe need:

$params['facet.field'][] = $facet_value;

but we shoudl rename these vars for clarity.

Also, t() strings should not have extra white space in them.

Also, the node type facet code should be moved out of the framework module.

I'm re-working this patch now.

not working yet, but getting there.

starting to work - needed uasort to preserve array keys, etc

more rewriting - removes block code duplication.

Also, we had some really odd/bad code:

$items = array_slice($items, 0, ($facet_display_limit == -1 ? NULL : $facet_display_limit));

Which meant we were requesting exgtra facets and then throwing them away. I modified the query so that we alsys add a default limit for the # of facets returned.

          // Add a default limit for fields where no limit was set.
          $params['facet.limit'] = variable_get('apachesolr_facet_query_limit_default', 20);

note lots of moving around here - net is only +39 lines thanks to reduced code duplication

committed to 6.x - hopefully I didn't miss anything