Complete rest of Title API

[bollwyvl]

Elevator Pitch

Add the rest of the (reasonable) Title (getter/)setters.

Motivation

When using a custom icon, it's also nice to have the tooltip/aria text info.

The other accessors are of perhaps less interest, but while changing the API, might as well be exhaustive.

Design Considerations

dataset would be a little weird, but still useful for some reason... perhaps for hiding stuff not created by a custom app, though presumably this could be done with class_name as well... need to see how they work together.