CRM-19925 Add Entity data and date format data to fields array on DAO.

CRM-19925 Add Entity data and date format data to fields array on  DAO.

    Per ticket this is intended to reduce in-code calculations by effectively
    caching some commonly used data into the DAO. In many cases civicrm
    compiles a large fields array & then twists itself up trying to distinguish the
    fields from each other. This makes the entity info readily available.

    Also moved to metadata is the format of core date fields.