Make a mock of Tyler's servers

[BryceStevenWilley]

As mentioned in #124 (comment), we should start making a Mock server for Tyler's EFM services. Ideally, we want something that:

• vets that we're sending the right XML data over, corresponding to the WSDL
• can send back a desired response according to some attribute in the sent XML
• can be run locally for folks (not interested in hosting our own free-standing server).

Leaning towards using SoapUI, which we can import a WSDL into and easily make responses (can do custom scripts too. Can also run it as a command line tool (installation is tricker, but still doable on Macs / Linux).

Partially started in https://github.com/SuffolkLITLab/EfileProxyServer/tree/soapui_mock, and in
https://github.com/SuffolkLITLab/EfileProxyServer/tree/mock_wsdl_refs.

[BryceStevenWilley]

Other related work on this:

• Add mock server files and lines for local tests #223, might refactor a bit more, but the bones of the changes needed are in there
• https://github.com/plocket/Efile_imposter_mock, some existing request / response files there
• https://stackoverflow.com/questions/51500738/content-is-not-allowed-in-prolog-error-yet-nothing-before-xml-declaration, error I ran into with some SoapUI calls, unclear why