Dev/python data

[austinschneider]

This PR aims to improve how we are packaging our data.

The main goals are:

• Have the package reference data from its resources directory
• Store generated data from DarkNews in the resources directory
• Version the cross sections, detector models, etc.
• Create a system for managing versions of these models in the context of the LIController and any other methods that perform some sort of automatic/default setup procedure

[austinschneider]

Currently this PR just fixes the python files within the project to use relative imports for things inside the package, adds some utilities for locating package resources, and installs resources into the python wheel.

[nickkamp1]

Currently this PR just fixes the python files within the project to use relative imports for things inside the package, adds some utilities for locating package resources, and installs resources into the python wheel.

Sounds good. Just verifying that I can run each example locally. So we'll have a separate branch for versioning?

[nickkamp1]

Examples are able to run locally. Approving PR