Prevent inadvertent CP/CPS checksum changes

[aarongable]

It turns out that the CCADB downloads a copy of the CP/CPS every time you file an "Add/Update Root Request" case. Every time it does so, it computes a checksum across the downloaded document, and if that checksum differs from the previously-downloaded version, it silently creates a duplicate of the document. This leads to surprising interactions in the CCADB UI.

We should develop a system to prevent unrelated changes -- such as minor scripting or CSS changes which affect the whole site -- from affecting the CP/CPS.

My suggestion: move the Certificate Repository (letsencrypt.org/certificate) and the Policy and Legal Repository (letsencrypt.org/repository) to a new subdomain like repository.letsencrypt.org. Then we can deploy that as a separate site with fully-static single-page (no external resources) CP/CPS docs.