Upgrade to Apache Lucene and Solr 4.8.0

Release notes:

• Lucene: http://lucene.apache.org/core/4_8_0/changes/Changes.html
• Solr: http://lucene.apache.org/solr/4_8_0/changes/Changes.html

We may need to look into:

<fields> and <types> tags have been deprecated. There is no longer any reason to keep them in the schema file, they may be safely removed. This allows intermixing of <fieldType>, <field> and <copyField> definitions if desired. Currently, these tags are supported so either style may be implemented. TBD is whether they'll be deprecated formally for 5.0