solr-schema.xml: More updates for Solr v4.x and hopefully with better filters.

solr-schema.xml: Replaced EnglishPorterFilterFactory with SnowballPorterFilterFactory

solr-schema: Version number is Solr's schema version, not Dovecot version.

fts: Redesigned/enhanced FTS API and how virtual plugin works with it. The changes include: - Only indexer process and "doveadm index" do FTS indexing now. Other processes connect to the indexer process via UNIX socket and request indexing a specific mailbox. - FTS backends can now index/search any search key. Current backends implement indexing for some specific header fields (Subject, From, To, Cc, Bcc), but it would also be possible to add indexing for e.g. message size or date. - CLucene support is fixed and fully functional. - Solr is split to "solr" and "solr_old" backends. The new "solr" backend supports the new header fields. It also uses mailbox GUIDs as mailbox identifiers, so that renaming a mailbox doesn't require reindexing. The "solr_old" uses the old Solr schema and doesn't support any new features.

solr-schema: Removed all references to unused "any" field.

solr: Don't use "any" copyfield, it doubles the index size. --HG-- branch : HEAD

fts: Added support for handling multiple namespaces. --HG-- branch : HEAD

fts-solr: Keep last_uid field updated containing the mailbox's last added UID. Use the last_uid document for finding the last added UID instead of creating a query with rows=1&sort=uid. It should be faster this way. --HG-- branch : HEAD

Moved Solr schema.xml to doc/. --HG-- branch : HEAD