Enable indexing of geospatial information in GeoJSON format.

[albig]

This patch adds the feature to index GeoJSON to the Solr index and to use the Spatial Search feature of Solr.

The GeoJSON is expected in MODS: ./mods:subject/mods:cartographics/mods:coordinate

The Solr schema has to be expanded by the following field and fieldType:

<fieldType name="geojson" class="solr.SpatialRecursivePrefixTreeFieldType" spatialContextFactory="Geo3D" geo="true" planetModel="WGS84" format="GeoJSON"/>
<field name="geom" type="geojson" indexed="true" stored="true" required="false" multiValued="false"/>

That's all :-)