Allow multiple dates in cvEntry

[LeWimbes]

This pull request introduces support for multiple dates for a single position. The feature reduces redundancy and saves space for recurring roles such as internships and teaching assistant positions.
To achieve this, a cvEntry is split into two columns: the first column contains the logo, title, society, description, and tags, while the second column displays the location and date(s) only.

[yunanwg]

Actually I thought of having this kind of feature, but put it on hold for complexity reason.

To me, it will be superb to have one entry with multiple dates; but that ideally if we have also have separate entryDescriptions. Imagine working as an intern first and then full-time will definitely have different scope and missions.

I haven't got the occasion to think this over, but definitely open to your idea!