Revisit import structure

[berland]

How modules inside pyscal are imported can be revisited.

• Solve import alerts on https://lgtm.com/projects/g/equinor/pyscal/alerts/?mode=list
• Should less modules be imported in __init__.py, to increase loading speed for those users who do not need everything? (There are users that actually requires speed)

It is somewhat tricky to get pyscal --version to work when bumping the import system

[berland]

If isort is used to sort all import statements, it results in circular import, illustrating fragility.