Solr 4.x backend upgrade (currently 4.6.1)

Initial pull request for review only, dont merge yet!

The main changes are:
- the upgrade of the included backend to Solr 4.6.1, 
- the corresponding ez publish custom solr  (elevator helper) request handler (changes in Java API in  Solr 4.x) 
- the addition of the softCommit parameter at appropriate places in the eZ Find classes and ezfind.ini setting
- activation of the transaction log (durability) which will replay non-committed changes upon restart of the Solr backend after a hard crash
- activation of the main index based spell check from 4.x (previously, a dedicated index was built upon commits, which added alot of overhead)
- separation of language dependent part of schema.xml into a dedicated file: makes upgrading and adding new languages much easier
- added analyzer definitions with for most common languages encountered in ezp projects with dedicated stopwords lists and sometimes other analyzer related files: ar, cjk, de, en, es, fi, fr, it, ja, nl, no, pt

Known issue: SolrCloud support is not complete at this moment because the custom request handler talks directly to a given core, not the Solr 4.x 'collection'.

Testing: manual and functional testing has been done