Bug 221337 [Markers] MarkerItem has too much API
We are exposing too much as API in MarkerItem. We should only provide getAtttributeValue and the methods that support PATH_ATTRIBUTE and NAME_ATTRIBUTE as they are tricky. Everything else needs to be pushed down to an internal class. We should mention the relevant IMarker constants for those removed.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/views/markers/MarkerCompletionField.java
* Return the constant that indicates whether or not the receiver is done
	 * 
	 * @param item
	 * @return 1 if it is done, 0 if it not and -1 if it cannot be determined.
	 */
	private int getDoneConstant(MarkerItem item) {
		int done = UNDEFINED;
		if (item.isConcrete()
				&& item.getAttributeValue(IMarker.USER_EDITABLE, true)) {
			done = NOT_DONE;
			if (item.getAttributeValue(IMarker.DONE, false)) {
				done = DONE;
			}
		}
		return done;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.internal.provisional.views.markers.api.MarkerField#getEditingSupport(org.eclipse.jface.viewers.ColumnViewer)
	 */
	public EditingSupport getEditingSupport(ColumnViewer viewer) {
		return new CompletionEditingSupport(viewer);
	}
	/**
	 * Get the image for item.
	 * 
	 * @param element
	 * @return Image
	 */