fixup auth mechanism for entire duration of app-utils.prepareApp().
greatly simplified test/app-utils.js.

number of tests in test/issuer.test.js appears to be halved, but it's just
b/c we're not logging into the backpack for every single assertion we're
doing; instead, we login once and do a bunch of things while logged in.
refactored test/app-utils.js a bit more
added test/login.test.js.
removed api-easy tests.