Cleanup/Refactor defaults.toml (& config checker)

[ericecook]

Currently each pool op has to rebase their own changes on top of the master defaults.toml whenever it gets changed, assuming they have any currencies not in the master version.

One possible solution (proposed by @crackfoo) is to make a defaults.toml.example - the downside is this requires users to create their own defaults.toml during installation

Another possible solution is to move currencies (and algo?) out to their own config file - resulting in fewer/clearer updates - the main downside there is that it doesn't resolve the core issue, just improves handling of it

[crackfoo]

Another possible solution is to allow a separate file that would also be read, but not required, but would override any like settings found in the default.

[ericecook]

@crackfoo that is how the the config.toml works - although it is required