This PR is the initial duplication of the WFE to create a WFE2
package. The rationale is briefly explained in `wfe2/README.md`.
Per #2822 this PR only lays the groundwork for further customization
and deduplication. Presently both the WFE and WFE2 are identical except
for the following configuration differences:
* The WFE offers HTTP and HTTPS on 4000 and 4430 respectively, the WFE2
offers HTTP on 4001 and 4431.
* The WFE has a debug port on 8000, the WFE2 uses the next free "8000
range port" and puts its debug service on 8013
Resolves https://github.com/letsencrypt/boulder/issues/2822
Jacob Hoffman-Andrews