Add orphan status indicator

[jsstevenson]

Grab from ChEMBL (as of v34):

The MOLECULE_DICTIONARY.ORPHAN field has been added to indicate whether a drug has orphan designation, i.e. intended for use against a rare condition (1 = yes, 0 = no, -1 = preclinical compound i.e. not a drug). This data is currently available for European Medicines Agency drugs only.

Could be available from other places, too.

[github-actions]

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