Update solver simflags

[Francesco Casella]

From the ​online documentation I read:

-lss=value or -lss value
    Value specifies the linear sparse solver method 

There is no indication of what are the admissible values, nor of the default. Please add them.

Later on I read the [following text ​https://openmodelica.org/doc/OpenModelicaUsersGuide/latest/simulationflags.html#simflag-nls]

-nls=value or -nls value

    Value specifies the nonlinear solver:

        hybrid
        kinsol
        newton
        mixed
        hybrid (Modification of the Powell hybrid method from minpack - former default solver)
        kinsol (sundials/kinsol - prototype implementation)
        newton (Newton Raphson - prototype implementation)
        homotopy (Damped Newton solver if failing case fixed-point and Newton homotopies are tried.)
        mixed (Mixed strategy. First the homotopy solver is tried and then as fallback the hybrid solver.)

Please remove the duplicates and update to the current status

[Francesco Casella]

Milestone changed to 1.13.0 since 1.12.0 was released

[Willi Braun]

Fixed in ​PR2222.