test(ngRoute): add test case for special params in redirectUrl

Make sure that :name? and :name* vars are properly interpolated in redirectUrl.
fix(ngRoute): improve interpolation of params in string

When the redirect path contains optional or special parameters the
interpolation function misses to remove them.

This is also the case for the auto-generated redirection where a slash
is appended or removed to a route.

Change the way parameters are interpolated in a string. Remove undefined
optional named groups and properly prepend a slash in case the named
group was starting with one.

Related to #5746.