Use TimePeriod for Media.mediaCreated
For older images it is often not exactly known when the picture was taken/created. In flora of Greece we sometimes have information such as "spring 1888" or "April 1986". This can not be handled with the current DateTime implementation.
Also the exact time is not always known, especially if you enter date manually.
Maybe we can have an extra hibernate user type which also allows to handle time if available.
Once this is finished, we need an update script and we need to update data from flora of Greece image import, images made by N. Turland. #7092
fix #7074 Change Media.mediaCreated to TimePeriod and make let PartialUserType support hour and minute
ref #7074 fix tests failing due to stricter format checking in Partial UserType