[!!!] Rename tx_solr.search.query.fields and tx_solr.search.query.fieldList

Rename the following configuration options:

* tx_solr.search.query.fields to tx_solr.search.query.queryFields and
* tx_solr.search.query.fieldList to tx_solr.search.query.returnFields

This makes naming more consistent and easier to understand for users new to Solr.
Remove empty line at EOF
[BUGFIX] Ignore useless, but valid values for sort indicator view helper