Replace pointer dates in `get-card` with zero values

[uhppoted]

Uninitialised controllers may not have the date/time set and there's always the possibility of corrupted/wrong values.

• [x] Replace From *Date in GetCardByIDResponse
• [x] Replace To *Date in GetCardByIDResponse
• [x] Replace From *Date in GetCardByIndexResponse
• [x] Replace To *Date in GetCardByIndexResponse
• [x] Replace From and To pointers in Card type
• [x] Unmarshal 00000000 to Date as ZeroDate
• [x] Unmarshal 00000000 to *Date as <nil>
• [x] Update uhppoted-lib
• [x] Update uhppoted-simulator
• [x] Update uhppote-cli
• [x] Update uhppoted-rest
• [x] uhppoted-rest get-cards should return cards with invalid from/to dates
• [x] uhppoted-rest get-acl should return cards with invalid from/to dates
• [x] uhppoted-rest put-acl should discard cards with invalid from/to dates
• [x] Update uhppoted-mqtt
• [x] uhppoted-mqtt get-cards should return cards with invalid from/to dates
• [x] uhppoted-mqtt get-acl should return cards with invalid from/to dates
• [x] uhppoted-mqtt compare-acl should include cards with invalid from/to dates
• [x] Update uhppoted-httpd
• [x] Update uhppoted-tunnel
• [x] Update uhppoted-dll
• [x] Update uhppoted-codegen
• [x] Update uhppoted-app-s3
• [x] Update uhppoted-app-sheets
• [x] Update uhppoted-app-wild-apricot
• [x] Include cards with invalid from and to dates in Docker simulator

[twystd]

And that's a wrap I think - pretty much everything updated to zero value card From and To fields and checked reasonably thoroughly.

Closing this as done, pending release v0.8.5.