[Zest 2.0] Ignore node size when calculating position in layout

The location of a node describes its top-left pixel, rather than its
center. When using layout algorithms that are based on the grid layout,
this causes the offset to be half the space between the rows and columns
plus the half the width and height of the nodes.
Latter is undesirable and may cause nodes to be partially moved outside
the client area.

The same issue can be observed in the other layout algorithms
(Spring/Tree/Radial) when fitting the nodes into the client area,
because the same mistake is repeated in the AlgorithmHelper class.

org.eclipse.zest.layouts/src/org/eclipse/zest/layouts/algorithms/AlgorithmHelper.java

@@ -56,9 +56,8 @@ public static void fitWithinBounds(EntityLayout[] entities, DisplayIndependentRe
 					entity.setSize(size.width, size.height);
 				}
 
-				location.x = destinationBounds.x + size.width / 2 + percentX * (destinationBounds.width - size.width);
-				location.y = destinationBounds.y + size.height / 2
-						+ percentY * (destinationBounds.height - size.height);
+				location.x = destinationBounds.x + percentX * (destinationBounds.width - size.width);
+				location.y = destinationBounds.y + percentY * (destinationBounds.height - size.height);
 				entity.setLocation(location.x, location.y);
 
 			} else if (resize && entity.isResizable()) {

org.eclipse.zest.layouts/src/org/eclipse/zest/layouts/algorithms/GridLayoutAlgorithm.java

@@ -385,9 +385,8 @@ protected synchronized void applyLayoutInternal(EntityLayout[] entitiesToLayout,
 						node.setSize(Math.max(childrenWidth, MIN_ENTITY_SIZE),
 								Math.max(childrenHeight, MIN_ENTITY_SIZE));
 					}
-					DisplayIndependentDimension size = node.getSize();
-					double xmove = bounds.x + j * colWidth + offsetX + size.width / 2;
-					double ymove = bounds.y + i * rowHeight + offsetY + size.height / 2;
+					double xmove = bounds.x + j * colWidth + offsetX;
+					double ymove = bounds.y + i * rowHeight + offsetY;
 					if (node.isMovable()) {
 						node.setLocation(xmove, ymove);
 					}