Pyhpo

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- Data update to ``hp/releases/2020-08-11``
- HPO: 15332 ==> 15530
- Genes: 4317 ==> 4366
- OMIM: 7675 ==> 7801
- Negative OMIM: 638 ==> 652
- ORPHANET: 3889 ==> 3956
- Negative ORPHANET: 240 ==> 255
- DECIPHER: 47 ==> 47
- Negative DECIPHER: 0 ==> 0

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- Added GraphIC similarity measure

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- Added Orphanet diseases to Annotation
- Added Decipher diseases to Annotation

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- Reworked BasicHPOSet
- Added omim_diseases to HPOSet
- Added distance method to similarity measurement
- Added equal measurement to HPOSet similarity

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- Refactored Ontology to act as a singleton
- Able to remove some weird dependencies when creating HPOSets
- Refactored some unit tests to only temporarily mock methods
- Performance improvements through using more cached objects
- Making HPOSet an actual set
- Adding BasicHPOSet
- Handling obsolete terms

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- Added serialization to HPO Term and HPO Set
- Option to remove modifier from HPO Set
- Changed Omim and Gene to be Singletons