Remove event long name

[fw42]

Closes https://github.com/fw42/cubecomp/issues/157.

This removes the "long name" attribute of events, from now on, they will only have a "name". This field was kinda useless in retrospect and sometimes the source of confusion.

Also, the "load" button for creating new events will now load the standard WCA event names.

For existing competitions, the long name will just be removed and the old short name will stay the same (so if you already created a competition with event names that are not the WCA standard event names, they will stay the way they are, not get automatically changed).

The only place on the competition website where you could even see the long name before was the registration form and the confirmation emails.

@cubizh @sauroux @Laura-O, all okay with this?

[cubizh]

Yes, that's great.

[Laura-O]

Looks good!