Processing of _route_ param should imply trailing '!' if not present

The SolrCloud _route_ param is supposed to end in a !. See https://cwiki.apache.org/confluence/display/solr/Distributed+Requests If you don't do it, you get different routing/hashing behavior that is bound to lead to some head scratching. We should instead not require a trailing exclamation (don't even mention it in the docs) and if it doesn't have one then we internally append one prior to applying it to the hashing algorithm (doc router).