Add the ability to set Action tooltip text

[sheeley820]

Could we add the ability to customize the tooltip on Actions? Should be a simple change. Basically just reading a title prop from the actions.

Action:

finish: {
  text: getTranslation('actions.finish'),
  onClick(e) {
    this._map.pm.Draw[button.jsClass]._finishShape(e);
  },
  title: "Foo"
}

Then when creating the action elements:

if (action.title)
        actionNode.setAttribute('title', action.title);

This would primarily be for implementing custom actions, but I think the getTranslation('actions.finish') text could be used for the built in actions, eliminating any need for new translation work.

Thanks for all the good work. Your plugin rocks.