69a05b0340
Expanding the selection from keyboard with Ctrl pressed should move in
the same way Ctrl-cursor does, but use the same selection anchor as
Shift-cursor does instead of always using the current cell.
This makes the expansion work much more intuitively in the grid, e.g.
pressing Shift-Ctrl-Down in
1 2
3 4
grid when 1 and 2 are selected now selects all the cells instead of
selecting 1 and 3 as it did before.