Servers from config

*Ready for someone to take over - feel free to contact me for any questions*

This is a start on the work to have Servers configured in config files rather than in the database. I have added Server config to config.groovy in a way that I think will work but feedback on this approach is welcomed. I have updated HostVerifier so that proxy requests use the new Server configuration to validate proxy URLs. There are other usages of Servers which haven't been changed over, yet.
Yeah, not a big deal, but it would have eliminated an annoying line in HostVerifier. Currently we have to add the baseLayerServer on it's own and then we add everything from `knownServers`. If it was in `knownServers` then it'd just get treated the same as all other servers.