Configuration

[JoeHowarth]

Way to set values via config file or CLI instead of by recompiling. Should make tuning things more straightforward.

Two use cases

1. Known, stable config options that must exist.

Should via struct with defaults perhaps

2. rapid prototyping of constants to avoid recompilation

String based hash table, allows dynamic adding and getting without having to change struct. Handle defaults, or lack thereof, on a case-by-case basis since not meant to be permanent.