R1:0902543fc8c4

Port MySQL settings to PHP

Summary:
- Ports MySQL settings to PHP.
- Removes "mysql.retries" -- this existed only because Magic Numbers Are Bad, but there is no concievable reason it should ever be set to anything other than 3.
- Introduced "Hidden" config, which isn't visible from the web (for SaaS, we'll just mark anything with secret keys as "hidden").
- Introduced "Masked" config, which will be masked in darkconsole once that gets updated.
- "Hidden" implies "Masked" and "Locked".
- Moved…