New configuration structure

[lfkeitel]

Part of issue #16 with plugins, the configuration needs to be reformatted into different sections. The defaults sections would be "core", where most of the current configuration would go, and "cheesto", which already exists. Eventually sections would be added for individual plugins. The "core" section could be split to "core-internal" for stuff like session timeout, session name, etc. And just "core" for stuff like the tagline, appTitle, and publicApiEnabled. Or the ApiEnabled setting could go in a section called "api". The cheestoEnabled setting would move to the Cheesto section of course and probably be renamed to simply "enabled". Basically provide some namespacing for settings.