should label be set on initialization?

[lucretiomsp]

on the buildingAWidget.md tutorial, the self label: 'Input' is called inside initialize. That makes a little bit complicated to change label after the widget creation.

we could have two different methods:
initializeLabel: that is called inside initialize , and then a label: method to call if we want to change the label text.

also, I find the name BlIntegerInputElement a little bit misleading, I suggest BlNumericalEntry