HubbardStructureData arent reachable in the AiiDA database widget

[AndresOrtegaGuerrero]

Since DFT+U is now available in the QeApp,
It is important to modify the logic of the AiiDAlab database widget to let the user find HubbardStructureData , for example if an optimization (or other plugin) generates HubbardStructureData.

We have to modify the logic but also double check that a user can use a HubbardStructureData, and being able to run other calculations with different the same structure with different Hubbard parameters or without them