Update to MOI v1

[blegat]

It is failing with

MethodError: no method matching JavaCall.JavaObject{Symbol("org.jacop.constraints.XeqC")}(::JavaCall.JavaObject{Symbol("org.jacop.core.IntVar")}, ::Int64)
  
  Closest candidates are:
    JavaCall.JavaObject{T}(::Tuple, ::Any...) where T
     @ JavaCall ~/.julia/packages/JavaCall/MlduK/src/core.jl:103
    JavaCall.JavaObject{T}(::Any) where T
     @ JavaCall ~/.julia/packages/JavaCall/MlduK/src/core.jl:96

and I have the same issue locally. Not sure what's the issue, I'm never used JuliaCall before.

[Azzaare]

I have updated JavaCall to v0.8 (last) but it doesn't solve it. It might be an issue with an update in JaCoP itself making breaking changes.
I tried to play a bit with fixing the errors but I stumbled upon some classes inheritance issues. Per say, XeqC is supposed to inherit from Constraint but we don't have inheritance in Julia.