View reciprocal space

[kbarros]

Refactor the Plotting module into multiple files. Introduces a dependence on the Brillouin.jl package, anticipating further support for #248.

Includes a function view_qspace for visualizing the Brillouin zone, its high-symmetry $q$-points, and other $q$-space objects.

This replaces private function viz_qqq_path. The visualization example in #310 becomes:

cryst = Sunny.hexagonal_crystal(; a=1, c=1)
path = q_space_path(cryst, [[0,0,0], [0,1,0]], 14)
params1 = Sunny.specify_transverse_binning(path, [1,1,0], [0,0,1], 0.2, 0.3)
view_qspace(cryst, params1)