[client] Shorten dates in transactions list + add day of week

This removes redundant information from the dates (month & year) and adds a textual reprensentation of the day of the week.

I chose to display the day on 3 chars because this helps having a constant width (else "Lundi" and "Mercredi" won't have the same width) and avoid layout issue.

Once we settle on the new layout (see Forum) about using 11 or 2 lines, on desktop or only mobile etc. we can revamp this to display maybe a full date such as "Monday 15th", but meanwhile I find it to be a simple and good enough approch.

Fix #776 (closed).