Add support for toolbar tooltip

[javier-godoy]

The toolbar icons should optionally support a tooltip. The actual title implementation can be provided by incubator-tooltip or title attribute.

[javier-godoy]

This feature is already implemented in 3.x

AppLayoutAddon/src/test/java/com/flowingcode/addons/applayout/ApplayoutDemoView.java

Lines 58 to 59 in e175420

	private final ToolbarIconButton miSettings =
	new ToolbarIconButton("Settings", "settings", this::openSettings);