configure PyBrowserId's SupportDocumentManager from syncserver.ini

This is a first attempt at addressing a local deployment of fxa-auth-server and syncserver:
the auth-server will use a self signed certificate so if local browserid verifiers checks the https certificate, it fails.
So I add the ability to disable verify. A better fix is to add the local certificate as trusted for requests down in PyBrowserId, but I don't know how, yet.
add this section to syncserver.ini to enable local https deployment for local testing of firefox sync:
[browserid]
backend = tokenserver.verifiers.LocalVerifier
audiences = *
verify = False