dev/https-everywhere

Add support for EFF's HTTPS-Everywhere rule format. It is split into a global plugin which reads the policy and then a per-instance plugin which applies it. The rules take some time to load and getting hit with this per-instance is non-ideal. It has variables to enable/disable support.

Currently, only navigation events are rewritten. A future branch will add support for event_sync (probably not named this; probably "request" depending on how conflicts with old configs is wanted) so that it can rewrite resource request URIs as well.