[Sketcher] Add some utility functions to Sketcher::Constraint

`involvesGeoId`, `invovesGeoIdAndPosId`, `substituteIndexAndPos`

src/Mod/Sketcher/App/Constraint.cpp

@@ -239,6 +239,25 @@ void Constraint::substituteIndex(int fromGeoId, int toGeoId)
     }
 }
 
+void Constraint::substituteIndexAndPos(int fromGeoId,
+                                       PointPos fromPosId,
+                                       int toGeoId,
+                                       PointPos toPosId)
+{
+    if (this->First == fromGeoId && this->FirstPos == fromPosId) {
+        this->First = toGeoId;
+        this->FirstPos = toPosId;
+    }
+    if (this->Second == fromGeoId && this->SecondPos == fromPosId) {
+        this->Second = toGeoId;
+        this->SecondPos = toPosId;
+    }
+    if (this->Third == fromGeoId && this->ThirdPos == fromPosId) {
+        this->Third = toGeoId;
+        this->ThirdPos = toPosId;
+    }
+}
+
 std::string Constraint::typeToString(ConstraintType type)
 {
     return type2str[type];