[Tournament] Allow a captain to edit his team's name and password

[Teanan]

(part of #33)

Not sure about the button appearance & location.

Also, should we forbid the change when the team is validated or when the tournament begins ?

[halfa]

IMHO the gear need a fix. The icon doesn't stand out - not like the button it should be - and the setting meaning is not that obvious.

• For team edit: maybe a pen-like symbol right of the team name ? In a blue button frame.
• For tournament registration: swap the gear for a button of some sort, or edit the image to stand out (in another PR?)

[halfa]

@Teanan the UI can be done later on, do you want to rebase and merge this one for the time being ?

[Teanan]

@halfa Yep, and I'll replace the gear tonight with an "edit team" label.
But I don't know when I'll be able to deploy in prod (currently on a train...)