Use named tuples for BookmarkVar values

[LeXofLeviafan]

I believe that using keywords/field names is better practice than magic numbers (i.e. row.title instead of row[2]), which is perfectly achievable when using named tuples (or their typed equivalent) instead of plain tuples – which is how the BookmarkVar type is defined at the moment.

This likely won't take much effort to implement, since converting a plain tuple to a named tuple is as simple as passing a (starred) tuple value to the constructor: BookmarkVar(*resultset[0]).