Create usage example with schemas and sample use-cases

[lundibundi]

Is your feature request related to a problem? Please describe. Currently the metaschema repo doesn't contain easily usable schemas that can be played around with to understand features and use-cases of it. They can only be "used" as a part of big https://github.com/metarhia/Example project that some may not need.

Describe the solution you'd like Add ./examples/ folder to the metaschema repo with run-scrips (Model.load('/path/to/schemas)) and schemas themselves.

/cc @tshemsedinov