ScoreAnalysis should not fail fast if the solver is unintialized

[ge0ffrey]

It's a pain as a user to have to work around this in practice:

java.lang.java.lang.IllegalArgumentException: java.lang.IllegalArgumentException: Cannot analyze solution (EmployeeSchedule@1198532872) as it is not initialized (-2828init/0hard/0soft).
Maybe run the solver first?

The only way to work around it is to update the solution first, calculate the score, check if its initialized and only then run the score analysis. All that code is boilerplate code. But if allowsUnassigned=false (default), then this boilerplate code is needed, just in case a CH doesn't finish on one particular dataset.
Let's make that boilerplate code unneeded.

• Check if the SDK's scoreAnalysis REST method doesn't work around this already, and remove it if that's the case

[ge0ffrey]

Proposal A put it into a constraintAnalysis

return new ScoreAnalysis {
   new ConstraintAnalysis { "Init score", HardSoftScore.ofInit(7) }
   ...
}

Con: the "init score" might be a valid constraint id already

Propsoal B add a field