Add module to work with schemas

[ssbarnea]

Based on original implementation made by @cidrblock this will allow us to reuse schema tools across multiple project, especially as the lower level python-jsonschema project does not produce identical results between runs.

The main reason for having our own wrapped on top of python-jsonschema project is that this library does not produce consistent results. Apparently the maintainer does not consider the need to always sort reported errors as needed, thus both ways (validate() and iter_errors()) to retrieve them can produce variable results between subsequent runs even when all input data is identical.

In follow-ups we will likely add a schema store class, so we will ensure we do not instantiate schemas more often than needed.

Related:

• validate does not raise errors in a predictable manner python-jsonschema/jsonschema#953
• "is not one of" error should happen only after checking type python-jsonschema/jsonschema#948
• Ensure proper sorting of list in error message python-jsonschema/jsonschema#940

[cidrblock]

Clever sorting method..... only because I learned about it the other day, if we ever need the others: https://docs.python.org/3/library/functools.html#functools.total_ordering