Automatically Expand Paths of single children #1063

In these cases, I expect all folders to open recursively
when clicking on com.wittmaxi.plugin

com.wittmaxi.plugin
 └─src
    └─org.foo.com
       └─Bar.java

A new feature in SWT allows for this feature, this PR enables that
feature in the Package Explorer.

Implements
eclipse-platform/eclipse.platform.ui#1063

org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java

@@ -256,6 +256,7 @@ private class PackageExplorerProblemTreeViewer extends ProblemTreeViewer {
 		public PackageExplorerProblemTreeViewer(Composite parent, int style) {
 			super(parent, style);
 			fPendingRefreshes= Collections.synchronizedList(new ArrayList<>());
+			setAutoExpandOnSingleChildLevels(ALL_LEVELS);
 		}
 		@Override
 		public void add(Object parentElement, Object... childElements) {
@@ -576,7 +577,7 @@ private void initFrameActions() {
 	}
 
 	private ProblemTreeViewer createViewer(Composite composite) {
-		return new PackageExplorerProblemTreeViewer(composite, SWT.MULTI | SWT.H_SCROLL | SWT.V_SCROLL);
+		new PackageExplorerProblemTreeViewer(composite, SWT.MULTI | SWT.H_SCROLL | SWT.V_SCROLL);
 	}
 
 	/**