Two New Methods for SvTreeListBox

Hello world,

Currently there is a RemoveSelection() method in SvTreeListBox which 
deletes the selected entry along with its children. But there is no 
method (that I could see) to delete an entry which is not currently 
selected. So you need to select each entry before removing, or get the 
pModel and call Remove method of it. Both cases have unnecessary overhead.

So I would like to add two new methods:

RemoveEntry(SvTreeListEntry* pEntry) //Remove with children
RemoveSingleEntry(SvTreeListEntry* pEntry) //Don't check for children

I appreciate suggestions if you think there is a better way. And feel 
free to use the methods after they get merged.

Cheers,
Muhammet