Completely overhaul test RP. One page, all APIs.

Still needs CSS and returnTo love, but should be much more functional than
the existing test RP.
Test RP: log options passed to watch/request/get
Add button for calling id.logout from test RP
Merge pull request #4182 from mozilla/overhaul-test-rp

Completely overhaul test RP. One page, all APIs.