Document how to create a configuration file and what other dependencies
you might need to get everything working.

Basically allow target URLs to contain @HOST@ string that would be
expanded to the servers hosts name/IP address (including [] in case of
IPv6) - this might be usefull in case of services running on different
port.

Redesign WebApps

Closes #6 and #4

See merge request !3

Change mock API to reflect discussed changes

See merge request !1