Name unique and default values

Covers:
* https://github.com/KSHSK/WAVED/issues/128 - Make sure all names (widget, dataset, etc.) are unique
* https://github.com/KSHSK/WAVED/issues/99 - Set default widget name
* https://github.com/KSHSK/WAVED/issues/142 - Open Properties Panel when new widget is added