Update path syntax for Express

It seems that * matches a literal * now, so we have to use a regular
expression.

Parentheses around a parameter no longer works (it causes it to match on
the parameter name literally) and I am not sure why we had it anyway as
it had no effect previously.

Matching with a leading / does not appear to work either, but we do not
need the leading / anyway since the proxy logic was changed to use the
whole path.  Consequently it will never be / anymore from what I can
tell but I left that check in just in case.  I turned it into a named
parameter as well, because that seems better.