Allow blindly trusted HTTPS domains to be globally configured in libphutil

Summary:
Last in a long chain of user requests. Lots of users use self-signed or otherwise goofy HTTPS certificates and don't have the expertise to configure a CA bundle. Let them just say "trust this domain implicitly, no matter what" in configuration.

The next diff will add an arc config option for this.

Test Plan: Added some `die()`, verified that the option in the next diff sends us down the right path.

Reviewers: btrahan

Reviewed By: btrahan

CC: hlau, aran

Differential Revision: https://secure.phabricator.com/D7130