Issue 301 redirects for Special:Search/searchterm

Issue 301 redirects for Special:Search/searchterm

Including the search term, which is PII, in the page title allows for
leaking this information through page view dumps. Instead of happily
handling these issue a 301 redirect to tell clients they should not
be issueing these requests, and should instead use the search query
parameter. Dumps at wikimedia remove 30[123] response codes from the
dump output so this will also stop leaking the PII.

Change-Id: Icce7cc4585e90742a8dd3513e7c9f7276e479cd7