Ovp-core

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* Add pyexcel to requirements

v1.2.8[unreleased]
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* Add SimpleAddressSerializar
* Add ADDRESS_SERIALIZER_TUPLE setting and get_serializer_tuple helper

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* Fix issue with serializers overridden by old serializers code
* Implemented Availability entity with model and serializer
* Add string formating to Availability
* Fix string formating to Availability, using get_*_display() to resolve values
* Implemented helpers to handle xls and csv responses
* Update pt_BR locale
* Add image field in causes
* Add image in causes serializer
* Add SimpleAddress model

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* Create SkillAssociationSerializer and CauseAssociationSerializer
* Fix locale setting on emails
* Add setting to disable emails

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* Add get_country_code() to GoogleAddress
* Add localization functionality to emails
* Add id to SkillSerializer and CauseSerializer
* Add required=False to name on SkillSerializer and CauseSerializer

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* Update pt_BR locale
* Add raw check on post_save signal for GoogleAddress