New styling of imports

[hakonanes]

I suggest a new "styling" of imports in the documentation (and test suite). Instead of importing functions and classes, we import modules.

Current:

from orix.quaternion import Rotation

Rotation.random()

New:

import orix.quaternion as oqu

oqu.Rotation.random()

If we're good at marking files as private (orix/quaternion/_misorientation.py etc.), users can look up of which functions and classes a module provides by tabbing with the cursor at oqu. etc.

Each module will then be importing accordingly:

import orix.data as oda
import orix.crystal_map as ocm
import orix.io as oio
import orix.measure as ome
import orix.plot as opl
import orix.projections as opr
import orix.quaternion as oqu
import orix.sampling as osa
import orix.vector as ove