HCP Stacking faults & Dislocations support

[thomas-rocke]

Features:

• Expansion of matscipy.utils.validate_cell to support HCP structures as inputs
• Modification of stacking fault + gamma surface tools to support HCP
• Support for dislocations in non-cubic systems (e.g. FCT)
• Implementation of screw and 60deg dislocations + dissociation in HCP
• Tests covering HCP dislocations
• Renaming e.g. CubicCrystalDislocation -> Dislocation
• Optimisation of disloc quadrupole kink construction (needed for HCP support)

TODO:

• Visualisation of kink quadrupole structures to check new system works in general
• Further validation of HCP and FCT dislocations
• Documentation on FCT & HCP dislocations
• Generic miller_to_spatial and bravais_to_spatial functions