Prevent expand and cnoffset params from propagating

Prevent expand and cnoffset params from propagating

The expand and cnoffset params in record summary might result in
unexpected behaviour if allowed to propagate by default, as mkurl()
enables, so stop them in their tracks.

Also, fix an overenthusiastic URI-encoding of subjects that led to a
space getting doubly-encoded (and thereby breaking searches).

Signed-off-by: Dan Scott <dan@coffeecode.net>