Improve UX for non-port-80 checks

[dmac]

Currently, to check a URL that's not on port 80, a new host must be created. This results in lots of duplicated information. The real world use-case driving this is we now have nsqd daemons running on all haggler boxes on a new port that we want to healthcheck. Ideally we would be able to do this by adding a single new path to the existing haggler role, but specifying the new port.

^-------- would like to specify port here

However, in the current UI the only way to do this is to create a new role, then duplicate all existing haggler hosts with the port appended to each of them.

etc.