BColumnListView: add SelectAll, AddToSelection(int startIndex, int endIndex) methods

[pulkomandy]

BColumnListView has a DeselectAll but no SelectAll method. It also has no way to programatically select multiple rows at once.

These are important because changing the selection results in sending the selection message. If "selecting all" in a list view with thousands of items, this would send the selection message a thousand times, instead of just once.

A way to add multiple rows at once would also be nice, for example with a start and end index, for the same reason.