Need validation of configuration files

[DavidMertz]

In working on module-noaa-stations, I/we misspelled "resource" in data_base section. The produced traceback is not informative.

Validations should include, I think:

• Informative message if YAML itself is misformed
• Use of any names that are not consistent with either built-in names (like "resource") or superclass definitions. E.g. how would this fail:

command_base:
  station_base:
    mixins: [stationWRONG]

Some informative message about the needed consistency would aid module developers

• Check data types within YAML config files. What is a nested dict, what must be a list, what must be a scalar value, etc. YAML doesn't enforce that (by design), but Zimagi requires narrower rules. Messages should describe those kinds of problems.

[adrianwebb]

Yep, need to work more on this. I have also started focusing on specification templating to make it easier to create standardized specifications for application systems, such as modules and models

[adrianwebb]

Related to: #51