No de-duplication when backend is offline

[SammyDelanghe]

When the backend of manual count is offline:

• there is no de-duplication of the laps atm: within 15 seconds it should only be possible to ad 1 lap to a team
• the de-duplication rule above should also work with multiple users are counting laps

[redfast00]

manual count could/should in broad terms work like the stations do and be pull based instead of push based. the problem is that browsers don't make pull-based api's easy, but the data flow conceptually could work like this

[redfast00]

I'll look into it after the OBUS event

[NuttyShrimp]

I've changed the search query for interfering laps in #49, now it searches for a lap at the timestamp of the pushed lap + and - the min difference needed between two laps

[NuttyShrimp]

So for caching the laps on the client and moving to a pull based system following tasks must be done:

Moved to #55