ENH: Add from_config_toml_path classmethod to vak.models.base.Model

[NickleDave]

after we do #601, #538, #345, as described in #614, because at that point it will be possible to load single model info from a config file

For this to work, the classmethod would need to know which table it's looking for a model name in, introspect its own class name, and then use that config, otherwise raise an error

Not sure if that's actually useful? Raising this issue for now to track