* fix deselecting items
* fix selection with the mouse and also holding down modifiers
* fix some more stuff I have already forgotten
* applied coding style in most places
* renamed private functions to be consistent
needs more work though, some stuff can definitely be
removed, some needs to be added
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@14932 a95241bf-73f2-0310-859d-f6bbb57e9c96