ui: Group graph nodes by file or namespace (issues #171, #439, #522)

* added buttons to enable grouping by file or namespace
* last used group settings saved to ApplicationSettings
* made groups hoverable/clickable on label only
* improved node hatching and override edge colors
* group overview lists

fortune cookie message = Seen with the eyes of love, everything gets a new meaning.

src/lib/component/controller/helper/BucketLayouter.cpp

@@ -194,7 +194,7 @@ void BucketLayouter::createBuckets(
 	}
 }
 
-void BucketLayouter::layoutBuckets()
+void BucketLayouter::layoutBuckets(bool addVerticalOffset)
 {
 	std::map<int, int> widths;
 	std::map<int, int> heights;
@@ -236,6 +236,11 @@ void BucketLayouter::layoutBuckets()
 				Bucket* midBucket = &m_buckets[0][0];
 				yOff = (heights[0] - midBucket->getHeight()) / 2 * -j;
 			}
+			// move every second bucket in a row slighly lower to avoid edges over nodes
+			else if (addVerticalOffset && std::abs(i) % 2 == 1)
+			{
+				yOff += GraphViewStyle::toGridGap(10);
+			}
 
 			bucket->layout(x, y + yOff, widths[i], heights[j]);
 			x += widths[i] + GraphViewStyle::toGridGap(85);