Set up relengapi docs to build from data_files, rather than package_data

This works great for *installed* code, but fails completely for `python
setup.py develop` installs, which go looking for the docs at `sys.prefix
/ 'relengapi-docs'`, but it's not there.
Handle development builds of the docs, too
update docs
update validate to handle docs
validate with build-docs --develop
Don't always 403 on permission fail if logged out.
Merge issue-85 (PR #85) - fixes #85
Merge djmitche/build-relengapi:issue83 (PR #83)

Conflicts:
	base/relengapi/blueprints/docs/__init__.py
Merge commit '111d54f' into slaveloan