[MonoDevelop] Coordinate system refactoring

[Levi Bard]

> What I want:
>
> To be able to write:
>
> Caret.Location = member.Location.
>
> Instead of:
> Caret.Location = new DocumentLocation (member.Location.Line - 1,
> member.Location.Column - 1);

Yes please!
I expect this to trigger a lot of regressions though, particularly in
the not-C# language bindings...
(Not an argument against)

> Should we use a 0 based coordinate system or a 1 based ?
>
> My preference would be a 0 based coordinte system for internal
> representation - my wife votes for a 1 based - therefore I need YOUR input.

I understand that it's nice to be able to think of Line 1, Column 1;
but making the unified coordinate system anything but zero-based is
begging for truckloads of off-by-one errors and array indices out of
bounds.