This patch include a new feature called "Field collapsing".
"Used in order to collapse a group of results with similar value for a given field to a single entry in the result set. Site collapsing is a special case of this, where all results for a given web site is collapsed into one or two entries in the result set, typically with an associated "more documents from this site" link. See also Duplicate detection."
The implementation add 3 new query parameters (SolrParams):
"collapse" set to true to enable collapsing.
"collapse.field" to choose the field used to group results
"collapse.max" to select how many continuous results are allowed before collapsing
TODO (in progress):
- More documentation (on source code)
- Test cases