Upgrade hadoop to 1.2.1 and add override method to upgrade

Julien,

I am wondering if we could upgrade the `master` branch hadoop dependency to 1.2.1. I noticed you did a similar update in `avro` branch.

 
All the tests are compiled successfully with `mvn install`

I also added support for indexing metadata as dynamic fields when the hadoop job parameter is defined. The dynamic fields are indexed with prefix 'attr_'.

Example: 

   ```hadoop jar solr/target/behemoth-solr-1.1-SNAPSHOT-job.jar com.digitalpebble.behemoth.solr.SOLRIndexerJob -Dsolr.metadata=true -Ddynamic.fields=true /output/behemoth_tika_lang http://localhost:8983/solr/collection1```