Ability to manually set the flights process state

[pschuler78]

In some cases, the club admin user should be able to set the flight process state to another value. E.g. during a glider camp, the flight will be invoiced from the camp chief, but the glider pilot entered the flight also in FLS for his flight book. So this flight might result in wrong invoicing. The club admin should be able to exclude such flights.
Another case could be, that the flight will be invoiced wrong because missing AccountingRuleFilters, so the club admin should edit the AccountingRuleFilters first and reset the relevant flights for another delivery process run.

The server offers two new WebAPI calls:

• GET api/v1/flightstates/processactions to receive the possible actions according the current flight process state
• PUT api/v1/flights/changeprocessstate/{flightId} to change a flights process state.

[pschuler78]

This implementation should be checked together with displaying/searching deliveries in client.