Bug 25845 Support for manually attaching source to a class path container
From Dejan: There is a work item on the ability to manually attach source to classpath entries managed by classpath container. We discussed it and we have workable options but we would like if we can have it by M3 because we want to start self-hosting using classpath containers ourselves.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/preferences/SourceAttachmentPropertyPage.java
return fSourceAttachmentBlock.createControl(composite);				
		} catch (CoreException e) {
			JavaPlugin.log(e);
			return createMessageContent(composite, PreferencesMessages.getString("SourceAttachmentPropertyPage.noarchive.message"));  
		}		
	}
	
	private Control createMessageContent(Composite composite, String message) {
		Composite inner= new Composite(composite, SWT.NONE);
		GridLayout layout= new GridLayout();
		layout.marginHeight= 0;
		layout.marginWidth= 0;		
		inner.setLayout(layout);
		
		GridData gd= new GridData(GridData.HORIZONTAL_ALIGN_FILL);
		gd.widthHint= convertWidthInCharsToPixels(80);
		
		Label label= new Label(inner, SWT.LEFT + SWT.WRAP);
		label.setText(message);
		label.setLayoutData(gd);
		return inner;
	}
	
	/*
	 * @see IPreferencePage#performOk
	 */
	public boolean performOk() {
		if (fSourceAttachmentBlock != null) {
			try {
				IRunnableWithProgress runnable= fSourceAttachmentBlock.getRunnable(fJarRoot.getJavaProject(), getShell());