RFE: Add initial static type hint checking support

[John L. Villalovos]

Add initial support for using static type hint checking.

Using the tool mypy:
http://mypy-lang.org/

This will require updating the tox.ini to run mypy in the [pep8] section.

And adding type hints into the code, at least a little amount to get things going.

[Jim Rollenhagen (jim-rollenhagen)]

Approved for ironic-lib in today's meeting, leaving tag as 'rfe' since it isn't approved for ironic proper.

[Ruby Loo (rloo)]

This was discussed in today's ironic meeting [1]. It wasn't clear whether this would be useful or not, and if useful, would it mean that we'd require all future code to support this?

We decided that it would be OK to try this out with ironic-lib. Depending on how that goes, we'll decide about whether to use it for other ironic projects, etc.

This RFE doesn't apply to ironic any more, just ironic-lib, so I applied the rfe-approved tag.

[1] starting at 17:33:53, http://eavesdrop.openstack.org/meetings/ironic/2016/ironic.2016-11-28-17.00.log.html