Fix #6 - Bind Storage Overview data

[axdelafuen]

Add subclass to User to fetch user metadata:

• Total boxes count
• Total items count (=> this only count the items entry in DB, and not count the "amount" field of items, dont know which data is expected)
• Total labels count

Add service / handler / route to get those data

linked issue: boks-boks-boks/boks-boks-boks#6

front PR: boks-boks-boks/boks-boks-boks#23

[viastolfi]

Thanks for the PR !

Some refacto + add the id into sended data so it can be displayed in front !

Merging, thanks again