Tabs bar headings should enlarge width (til a max) if text is larger

[brauliodiez]

The best way to overcome with the current limitation is with an example

Let's add the following fields

Datos Generales, Datos económicos, Certificaciones, Notas

The result:

There is not an straight forward solution, we should:

• Start with the initial fixed size for each tab.
• Extract the width avaiable to enlarge this tabs (full main rectangle width minus some margins).
• Calculate each text field width needed.
• Start with the first tab an provide a bigger width to the tabs that need that