SBGN Brick multimer edge connection workaround

  Since cytoscape automatically changes the rendered bounding box
  without changing the node's data properties, multimer edges on
  sbgn bricks were rendering tilted. This commit is a workaround
  to make the edges look better in previews.

  This is not a complete solution to the problem.

  Addresses iVis-at-Bilkent/newt#662.

src/utilities/element-utilities-extender-factory.js

@@ -860,6 +860,7 @@ module.exports = function () {
       const widthPerChar = 6;
       const tilingPaddingVertical = 15;
       const tilingPaddingHorizontal = 15;
+      const multimerOffset = 6;
 
       cy.startBatch();
 
@@ -960,6 +961,9 @@ module.exports = function () {
         const regulatorMultimer = regulator.multimer;
 
         let xPosOfRegulator = processPosition.x;
+        if (regulatorMultimer.enabled && orientation === "horizontal") {
+          xPosOfRegulator -= multimerOffset;
+        }
         let yPosOfRegulator = processPosition.y - ((processHeight / 2) + (regulatorHeight / 2) + edgeLength); 
 
         nodePosition = {
@@ -1027,6 +1031,7 @@ module.exports = function () {
       const processPortsOrdering = orientation === "vertical" ? "T-to-B" : "L-to-R";
       const minInfoboxDimension = 20;
       const widthPerChar = 6;
+      const multimerOffset = 6;
 
       cy.startBatch();
 
@@ -1101,6 +1106,9 @@ module.exports = function () {
         const regulatorEdgeType = regulator.edgeType;
 
         let xPosOfRegulator = processPosition.x;
+        if (regulatorMultimer.enabled && orientation === "horizontal") {
+          xPosOfRegulator -= multimerOffset;
+        }
         let yPosOfRegulator = processPosition.y - ((processHeight / 2) + (regulatorHeight / 2) + edgeLength); 
 
         nodePosition = {
@@ -1168,6 +1176,7 @@ module.exports = function () {
       const processPortsOrdering = orientation === "vertical" ? "T-to-B" : "L-to-R";
       const minInfoboxDimension = 20;
       const widthPerChar = 6;
+      const multimerOffset = 6;
 
       cy.startBatch();
 
@@ -1321,6 +1330,9 @@ module.exports = function () {
         const regulatorName = regulator.name;
         const regulatorType = regulator.type;
         let xPosOfRegulator = processPosition.x;
+        if (regulatorMultimer.enabled && orientation === "horizontal") {
+          xPosOfRegulator -= multimerOffset;
+        }
         let yPosOfRegulator = processPosition.y - ((processHeight / 2) + (regulatorHeight / 2) + edgeLength); 
 
         nodePosition = {
@@ -1397,11 +1409,11 @@ module.exports = function () {
       const regulatorHeight = defaultRegulatorProperties.height || 50;
       const processPosition = elementUtilities.convertToModelPosition({x: cy.width() / 2, y: cy.height() / 2});
       const tilingPaddingVertical = 15;
-      const tilingPaddingHorizontal = 15;
       const edgeLength = 30;
       const processLeftSideEdgeType = reversible ? "production" : "consumption";
       const processRightSideEdgeType = "production";
       const processPortsOrdering = orientation === "vertical" ? "T-to-B" : "L-to-R";
+      const multimerOffset = 6;
 
       cy.startBatch();
       if (!elementUtilities.getMapType()) {
@@ -1494,6 +1506,9 @@ module.exports = function () {
         const regulatorName = regulator.name;
         const regulatorType = regulator.type;
         let xPosOfRegulator = processPosition.x;
+        if (regulatorMultimer.enabled && orientation === "horizontal") {
+          xPosOfRegulator -= multimerOffset;
+        }
         let yPosOfRegulator = processPosition.y - ((processHeight / 2) + (regulatorHeight / 2) + edgeLength); 
 
         let nodePosition = {