Pickling subtypes, individuals and *families*

[daffidwilde]

Refactor the subtype process so that they can be stored via pickle and json by introducing a new Family class that handles a Distribution class' subtypes.

[coveralls]

Pull Request Test Coverage Report for Build 107

• 191 of 191 (100.0%) changed or added relevant lines in 10 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 92:	0.0%
Covered Lines:	605
Relevant Lines:	605

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💛 - Coveralls