List numbering should be restarted when copied list is pasted after content that is not in a list.

Steps to reproduce:
1. Create a file with a list, a blank line, some text, and another blank line
2. Copy the list
3. Paste it on the blank line directly after the list
Expected: The items are added to the end of the existing list
Observed: The items are added to the end of the existing list
4. Paste it on the blank line after the text
Expected: The items are added to a new list and start numbering at 1
Observed: The items are added to the existing list and start numbering at 7

Workaround:
private void RadRichTextBox_CommandExecuting(object sender, Telerik.Windows.Documents.RichTextBoxCommands.CommandExecutingEventArgs e)
{
    if (e.Command is PasteCommand)
    {
        DocumentPosition position = new DocumentPosition(this.radRichTextBox.Document);
        position.MoveToPosition(this.radRichTextBox.Document.CaretPosition);
        position.MoveUp();
        Paragraph previousParagraph = position.GetCurrentParagraphBox().AssociatedParagraph;
        if (previousParagraph.IsInList)
        {
            // We shouldn't restart the numbering when the previous paragraph is in a list.
            return;
        }

        RadDocument doc = ClipboardEx.GetDocument().ToDocument();
        Paragraph firstParagraph = doc.EnumerateChildrenOfType<Paragraph>().First();
        if (firstParagraph != null && firstParagraph.IsInList)
        {
            RadDocumentEditor editor = new RadDocumentEditor(doc);
            editor.Document.CaretPosition.MoveToStartOfDocumentElement(firstParagraph);
            editor.RestartListNumbering();
        }

        this.radRichTextBox.InsertFragment(new DocumentFragment(doc));
        e.Cancel = true;
    }
}