Automate date parsing

[Chalarangelo]

Motivation

Having to cast date values to new Date() manually is rather inefficient in some cases. We could handle this internally for date-like string values.

Proposal

Add a simple way for date type fields to parse their value without throwing a validation error. This will only be possible if the given value is a string and can be cast to a valid date value.

Considerations

Numeric values could be valid in some cases, too.

[Chalarangelo]

No validation added for strings etc., dates will be parsed automatically but only for singular date fields, not dateArray fields.