Overhaul interfaces

[shyamd]

This PR overhauls all the interface code including the ZSL Generator and the substrate matcher:

• Creates a new Interface data class in core
• Moves interface algorithm to analysis.interfaces; imports and warnings in the old modules ensure they should still work
• Cleans up ZSLGenerator and SubstrateAnalyzer by implementing functional dataclasses for the matches making it easier to understand how to extra important quantities like the strain and transformation matrix
• Implements a CoherentInterfaceBuilder which builds Interface objects using the lattice matching of the Zur and McGill algorithm

[coveralls]

Coverage decreased (-0.6%) to 83.075% when pulling 0aa785d on shyamd:interfaces into 37d8c1e on materialsproject:master.

[mkhorton]

Nice PR!