Allow the use of several timers in an event

[Amaras]

During the setup for an event with several tournaments which don't have the same start times or cadence, I realized that only one timer is available.

Current solution

One of two possible solutions:

1. Spin up two different servers with different ports, and set up two events with a distinct timer.
2. Use one timer and add events for each (which can interfere with each other).

Proposed solution

Allow the use of distinct timers in an event (undecided syntax) If several timers are configured, use show_timer = <timer_id> and disallow show_timer = on in screens and tournaments

[pascalaubry]

Possible in 2.4.0.