Bug 161401 [Viewers] Tweak ColumnViewer-API
- Rename getRowPart(Point point) => getViewerRow() - Rename getCell(Point point) => getViewerCell() - Rename setViewerColumn(final int columnIndex, ViewerColumn viewer) => setupEditingSupport - Make setupEditingSupport() private no one from external needs to use this API to set the EditingSupport for an ViewerColumn
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/TreeViewer.java
private static final String VIRTUAL_DISPOSE_KEY = Policy.JFACE
			+ ".DISPOSE_LISTENER"; 
	/**
	 * Internal tree viewer implementation.
	 */
	private TreeEditorImpl treeViewerImpl;
	/**
	 * This viewer's control.
	 */
	private Tree tree;
	/**
	 * This viewer's tree editor.
	 */
	private TreeEditor treeEditor;
	/**
	 * Flag for whether the tree has been disposed of.
	 */
	private boolean treeIsDisposed = false;
	private boolean contentProviderIsLazy;