Booth can be replaced with any alias by replacing it in alias.en.yml. This change is introduced as some events do not use booth but uses other words such as stand.
If the registration period is over then speakers of confirmed events
can't register anymore. They should be able to, since they are gonna be
there anyway.
* Allow the speakers of confirmed events to register regardless of the
registration period
* Provision for registrations of confirmed speakers, so as not to
exceed the registration limit
* Add scope for registered speakers
Fix#829 and fix#802
