Commit portfix version of snmpit and the Port module.
This commit pushes the changes located in the temporary snmpit_portfix subdirectory into the mainline snmpit_test directory, and updates db/Ports.pm with the 'portfix' changes. These changes ensure better consistency with port lookup/resolution. In particular, interswitch trunk lookup will return the switch-local side of the link. This commit also adds an installer script to cleanup the temporary files introduced for burning in the snmpit_portfix changes.