Prevent Event, WikiPage and Thread from being pasted places where they don't

belong.  This allows chained method calls to "getMyParent", getParent, getWiki, getCalendar, etc.
to work.
Adds the new canPaste and validParent method to Asset and AssetClipboard.

lib/WebGUI/Asset/Post/Thread.pm

@@ -868,6 +868,22 @@ sub updateThreadRating {
 }
 
 
+#-------------------------------------------------------------------
+
+=head2 validParent
+
+Make sure that the current session asset is a CS for pasting and adding checks.
+
+This is a class method.
+
+=cut
+
+sub validParent {
+    my $class   = shift;
+    my $session = shift;
+    return $session->asset->isa('WebGUI::Asset::Wobject::Collaboration');
+}
+
 #-------------------------------------------------------------------
 sub view {
     my $self = shift;