Add PPAN properties calculation

[coveralls]

Pull Request Test Coverage Report for Build 792

• 208 of 235 (88.51%) changed or added relevant lines in 11 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.01%) to 88.695%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
aiida_crystal17/calculations/prop_doss.py	3	5	60.0%
aiida_crystal17/parsers/raw/crystal_ppan.py	35	39	89.74%
aiida_crystal17/parsers/raw/prop_inputs.py	17	22	77.27%
aiida_crystal17/parsers/cry_ppan.py	60	76	78.95%
<!--	Total:	208	235	88.51%	-->

Totals
Change from base Build 784:	0.01%
Covered Lines:	7359
Relevant Lines:	8297

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💛 - Coveralls