Support elevate.q in QueryElevationComponent

QueryElevationComponent uses the query in parameter to match the elevate.xml.

"query text" from elevate.xml
: has to match the query (q=...). So in this case, elevation works only for
: http://localhost:8080/solr/elevate?q=brain, but not for
: http://localhost:8080/solr/elevate?q=indexingabstract:brain type of queries.

But sometimes, the query is more complex, we may use some nested query or complexphrase.

it would also be fairly easy to make QEC support an "elevate.q" param similar to how there is a "spellcheck.q" param and a "hl.q" param to let the client specify an alternate, simplified, string for the feature to use.

Conten copied from:
http://lucene.472066.n3.nabble.com/Problems-with-elevation-component-configuration-td3993204.html