WPCOM Atomic compatibility

[NickGreen]

Investigate and implement changes to Safety Net which make the plugin work with WPCOM infrastructure, Atomic sites specifically.

we shouldn't disable Jetpack or else logging in doesn't work. And probably not scrub Jetpack options.

[NickGreen]

This should be fixed here: #134

I've still disabled a couple of Jetpack modules, such as subscriptions, because we don't want anything getting sent out to users, but have left the secrets and private jetpack options intact. Closing this out for now.