Add various plot funcs to common namespace

Author: rpep

fidimag/common/__init__.py

@@ -4,3 +4,4 @@
 from .citation import citation
 from .cuboid_mesh import CuboidMesh
 #from .neb_cartesian import NEB_Sundials
+from .plot import plot, plot_micro, plot_atom_hex, plot_atom_cub