Limit number of total registrants per event

[mathysp]

When creating events you sometimes deal with a limited amount of seats.

Using RNG we can control the amount of registrations, and the number of registrants per registration. But we can not limit an event on number of registrants.

Proposed solution would be a simple input field: maximum number of registrants.

[dpi]

Under consideration for 1.4

[dpi]

Related: http://drupal.stackexchange.com/questions/230456/drupal-rng-trouble-with-maximum-registrants/230953