Adaptively autocomplete distribution or module names when finding a queue

If the user types a colon, we assume they're looking for a module name
and switch to mapping modules to distributions via api.metacpan.org.

If the user hasn't yet typed a colon, we preserve the long-standing
expectation of distribution names and autocomplete against rt.cpan.org
queue names.

This means that typing "App::Prove" finds you Test-Harness and typing
"LWP::U" finds you libwww-perl.  It also ensures that typing "libwww"
autocompletes to libwww-perl for anyone familiar with rt.cpan.org's
historical expectations.