Lucene / ImportantDocument boosting class does not work due to Lucene 4.1 update

[fxp]

Due to Lucene 4.1 changes in the API.

If you previously used Document.setBoost, you must now pre-multiply the document boost into each Field.setBoost.

Applied on Lucene update but need some fix.

The class needs to loop over the xml to be indexed instead of the (now empty) doc to properly compute the boost factor for the document. Then boost could be applied to all fields using Field.setBoost instead of Document.setBoost.

Also boost is always set to 1 ​https://github.com/geonetwork/core-geonetwork/blob/master/web/src/main/java/org/fao/geonet/kernel/search/SearchManager.java#L1409

We need to avoid "java.lang.IllegalArgumentException: You cannot set an index-time boost on an unindexed field, or one that omits norms".

[fxp]

master commit 1cace58d7d1cdcfb00673aceb6bf1df46f4d5dbe