OCA Explorer: Add support for handling the Aries special "dateint" and "Unix Time" data types

[swcurran]

Add support for displaying attributes as dates, as outlined in the OCA for Aries RFC.

Specifically:

• detect the date types
• for display, convert them to their components parts (e.g. YYYY, MM, DD, HH, MM, SS)
• display them according to the user and language settings of the user.
  • Not sure how to do that in OCA Explorer vs. in the Bifold Wallet -- this may need a further discussion