Refactor authentication into part of relengapi proper.

This removes the dependency on Flask-Principal, and focuses all auth
info on `current_user`.

Token auth is temporarily broken.
Set permissions on HumanUser
Move authorization stuff into plugins, too
fix up tokenauth
update account template
require blinker too
remove unused 'make_support_class' method
Allow other relengapi projects to document themselves
fix typo and pep8, include the proper files in sdist and installs
remove unused variable docs_patterns
Merge djmitche/build-relengapi:issue23 (PR #23)
Merge djmitche/build-relengapi:issue40 (PR #40)
Merge branch 'master' into issue2
update docs tests after merge from master
Add tests for relengapi.celery