[TECH SUPPORT] LPS-42541 Portlet title defaults to empty String

Hi Tamás,

I'm resending the pull after discussing the logic with Zsigmond. Now on the UI the default portlet titles get populated so the user can see which title that we fallback to if it is not changed. There is a little tweak to save disk space: the portlet title gets removed from the portlet preferences during the update action (UpdateLookAndFeelAction) if the new custom title would be the same as the default one. Also, the fallback logic has been removed from PortletConfigurationUtil#getPortletTitle as it does not make sense anymore.

Please review the changes. Please make sure it will be reviewed by Jorge as per his request.

Thanks,
Ákos