LP#1811685: qtype CGI parameter checking

LP#1811685: qtype CGI parameter checking

With this commit we throw away searches with invalid qtype value based
on configured classes and aliases.  Invalid qtype values have been seen
in the wild as part of attempted (but failed) SQL injection attacks, so
we will tighten up what we accept.

As an additional (unrelated) bonus, this commit also avoids prepending
the search class on basic search when the class (from qytpe) is not
exactly "keyword".

Signed-off-by: Mike Rylander <mrylander@gmail.com>
Signed-off-by: Jason Stephenson <jason@sigio.com>
Signed-off-by: Galen Charlton <gmc@equinoxOLI.org>