Clean up config utils

[zcox]

The utils we provide for configs need to be improved in a few ways:

1. Need to support all configs. Defining all of them is tedious, can we automate this somehow?
2. Initially each config had a case class, and a companion object with an implicit. A simpler idiom is just the object with an apply constructor, or pre-defined values in some cases. Refactor to simpler approach.