Add 'Display invoice date' option

[Terminator-Barbapapa]

The ‘Date’ column displays the invoice date and therefore reflects your ‘Display invoice date’ setting. This can be confusing for users: https://wordpress.org/support/topic/invoice-number-progression-2/#post-15849210

It might be useful if we can display which option for the 'Display invoice date' was set when generating the invoice. This of course would also apply to the proforma and credit note.