Rewrite how client gets configured

Environment variables don't get sent when the app
is run without the debugger. Rather than
continuing down this route, find something less
complex and hidden (launch arguments made sense
for tests--supposed cli integration, whereas this
is different) ...

Use an Info.plist instead, with constant keys for
safety. They are the conventional form of
static configuration storage for apps.
Fix client build scheme for tests

Includes minor renaming.