Allow customizable bean mapping for QueryResponse.getBeans(..)

The mechanism for getting beans is rather limited - only classes @Field-annotated fields.

Imaging the following subprojects:

• common
• search

And you want to reuse a class from common as a result from a solr search. You should either duplicate the structure or make common depend on solrj. Neither are desirable.

So, my suggestion:

• introduce a pluggable mechanism for bean resolution. Currently it is impossible - it uses private methods and private inner classes. (This will be useful for custom conversions, because the existing one fails in some cases where BeanUtils.copyProperties works.)
• allow externalized (xml) configuration
• allow detecting all fields, annotated or not (off by default)