Add minimum payu version check

[jo-basevi]

Add a payu_minimum_version option to config.yaml. This runs a check at the start of the Experimet.setup comparing the current payu version and raises a RuntimeError if version is earlier than the configured minimum version.

I added a dependency on the packaging lib to parse and compare versions, which seems to the recommended library for parsing version strings (https://stackoverflow.com/a/11887885, https://setuptools.pypa.io/en/latest/deprecated/distutils-legacy.html#prefer-setuptools). I could do some regex parsing, but this library can handle already handles versions like 1.0, v0.1, 1.0.0+4.gabc1234 etc. So hopefully it'll be less buggy and will be able to support future version formats..

I added the check to the start of the setup method to the experiment class which seemed the logical place for it at the moment. So unfortunately it's adding more logic to an already long file. I thought about adding a setup.py file for setup helper methods, but I am not sure whether that'll make it better having one file for one small function?

Closes #147

[coveralls]

coverage: 56.106% (+0.3%) from 55.782%
when pulling a6bed42 on ACCESS-NRI:147-add-minimum-payu-version
into c07eeaf on payu-org:master.

[aidanheerdegen]

Just a single change, but feel free to push back if you disagree.

[aidanheerdegen]

Looks great! Thanks Jo. merge if you're happy to do so.