Allow entering date of entries

[Sebazzz]

This would allow to generate more accurate reports, enable sending a weekly digest, etc.

Basically much of the ordering system would be replaced by the date system. Dates do the ordering, if you have multiple entries on one day, you can specify an optional time to order.

Input of date is set to "now" by default, but can be easily changed to "yesterday" or a custom date if required.

Data migration would be by the ordering, then if realistic/possible it would use the insert timestamp as the date. That should in a functional sense retain the correct ordering.