change update order from: add new key; remove its children from mTopLevels and mKeysByNonExistingParent; add children to new parent to remove children from all indexes; add new key; re-add its children.

This avoids an inconsistent state when a key was just added but its children are still in mTopLevels (which leads to index( x, y, QModelIndex() ).parent() == justAddedKey )

svn path=/trunk/KDE/kdepim/kleopatra/; revision=796743