add entities / entity relations

[OriHoch]

• rename רשויות to ישויות
• allow to link dataset to primary entities and secondary entities - show this distinction in entities tab of dataset
• each entity has entity type, for example: budgetkey company entity / oknesset MK entity etc.. linking to the source of the entity
• in datasets search - allow to filter only on entities which are related as primary entities. and only show datasets in search results which are linked as primary entities. number should indicate datasets linked as primary