Renamed employee status for better clarity (February)

We have removed "planned" as an employee status, which was used for employees that were entered manually instead of synced. This resulted in mixing two questions together: "is someone active" and "is someone coming from the HRIS". We also removed "hired" which followed a similar idea.

Instead we introduce a new status "future start", so that each status is purely based on contract dates. Non-synced employees can be found for example by filtering for "no name" employees.

We've also renamed badges on the contracts overview to "Current" and "Future contract", to more clearly distinguish between the overall employee status.