Add autocompletion to EmptySubstructureContent

- Add substitute menu of ISubstructureContent to its editor
- Make substitute menu of EmptySubstructureContent empty because it
  should not appear in menus (only used in element factories)

Author: apann

code/languages/org.iets3.opensource/languages/org.iets3.components.core/models/editor.mps

@@ -109,12 +109,18 @@
         <property id="5944657839012629576" name="presentation" index="2BUmq6" />
       </concept>
       <concept id="1239814640496" name="jetbrains.mps.lang.editor.structure.CellLayout_VerticalGrid" flags="nn" index="2EHx9g" />
+      <concept id="1164824717996" name="jetbrains.mps.lang.editor.structure.CellMenuDescriptor" flags="ng" index="OXEIz">
+        <child id="1164824815888" name="cellMenuPart" index="OY2wv" />
+      </concept>
       <concept id="1078938745671" name="jetbrains.mps.lang.editor.structure.EditorComponentDeclaration" flags="ig" index="PKFIW">
         <child id="7033942394258392116" name="overridenEditorComponent" index="1PM95z" />
       </concept>
       <concept id="1078939183254" name="jetbrains.mps.lang.editor.structure.CellModel_Component" flags="sg" stub="3162947552742194261" index="PMmxH">
         <reference id="1078939183255" name="editorComponent" index="PMmxG" />
       </concept>
+      <concept id="1164914519156" name="jetbrains.mps.lang.editor.structure.CellMenuPart_ReplaceNode_CustomNodeConcept" flags="ng" index="UkePV">
+        <reference id="1164914727930" name="replacementConcept" index="Ul1FP" />
+      </concept>
       <concept id="1186402211651" name="jetbrains.mps.lang.editor.structure.StyleSheet" flags="ng" index="V5hpn">
         <child id="1186402402630" name="styles" index="V601i" />
       </concept>
@@ -176,6 +182,7 @@
       <concept id="1073389214265" name="jetbrains.mps.lang.editor.structure.EditorCellModel" flags="ng" index="3EYTF0">
         <reference id="1139959269582" name="actionMap" index="1ERwB7" />
         <child id="1142887637401" name="renderingCondition" index="pqm2j" />
+        <child id="1164826688380" name="menuDescriptor" index="P5bDN" />
       </concept>
       <concept id="1073389446423" name="jetbrains.mps.lang.editor.structure.CellModel_Collection" flags="sn" stub="3013115976261988961" index="3EZMnI">
         <property id="1160590353935" name="usesFolding" index="S$Qs1" />
@@ -1778,6 +1785,11 @@
       <node concept="VPxyj" id="siw10FjaRC" role="3F10Kt">
         <property role="VOm3f" value="true" />
       </node>
+      <node concept="OXEIz" id="3JN4mhXK7vV" role="P5bDN">
+        <node concept="UkePV" id="3JN4mhXK7vX" role="OY2wv">
+          <ref role="Ul1FP" to="w9y2:siw10FiR6c" resolve="ISubstructureContent" />
+        </node>
+      </node>
     </node>
   </node>
   <node concept="24kQdi" id="siw10FjeBC">
@@ -13805,5 +13817,10 @@
       <property role="3F0ifm" value="Workaround to fix contributions to BaseConcept generated by grammarCells." />
     </node>
   </node>
+  <node concept="22mcaB" id="3JN4mhXK73Z">
+    <property role="3GE5qa" value="components.substructure" />
+    <ref role="aqKnT" to="w9y2:siw10FjaPn" resolve="EmptySubstructureContent" />
+    <node concept="22hDWj" id="3JN4mhXK740" role="22hAXT" />
+  </node>
 </model>