Add expire columns to main view

[scop]

i have several certificate in a wallet and one feature i miss is a quick way to see when will the certificate expire (or if they are already expired) without having to click on each certificate. A simple column with the expire date would be perfect.
A column for fingerprint and for the subject would even better, so one could see duplicate certs (both different versions or exactly the same certificate)

Thanks for portecle! :)

Reported by: higuita