[FEM] Elmer: set constraints for solver systems

- set constraints according to the Elmer docs (no conversion necessary, existing properties just stay integers)

src/Mod/Fem/femsolver/elmer/equations/linear.py

@@ -66,7 +66,7 @@ class Proxy(equation.Proxy):
         super(Proxy, self).__init__(obj)
 
         obj.addProperty(
-            "App::PropertyInteger",
+            "App::PropertyIntegerConstraint",
             "BiCGstablDegree",
             "Linear System",
             "Polynom degree for iterative method 'BiCGstabl'"
@@ -78,7 +78,7 @@ class Proxy(equation.Proxy):
             ""
         )
         obj.addProperty(
-            "App::PropertyInteger",
+            "App::PropertyIntegerConstraint",
             "LinearIterations",
             "Linear System",
             ""
@@ -130,9 +130,9 @@ class Proxy(equation.Proxy):
             ""
         )
         
-        obj.BiCGstablDegree = 2
+        obj.BiCGstablDegree = (2, 2, 10, 1)
         obj.LinearDirectMethod = LINEAR_DIRECT
-        obj.LinearIterations = 500
+        obj.LinearIterations = (500, 1, int(1e6), 50)
         obj.LinearIterativeMethod = LINEAR_ITERATIVE
         obj.LinearIterativeMethod = "BiCGStab"
         obj.LinearPreconditioning = LINEAR_PRECONDITIONING

src/Mod/Fem/femsolver/elmer/equations/nonlinear.py

@@ -42,13 +42,13 @@ class Proxy(linear.Proxy):
         super(Proxy, self).__init__(obj)
 
         obj.addProperty(
-            "App::PropertyInteger",
+            "App::PropertyIntegerConstraint",
             "NonlinearIterations",
             "Nonlinear System",
             "Maximum number of iterations"
         )
         obj.addProperty(
-            "App::PropertyInteger",
+            "App::PropertyIntegerConstraint",
             "NonlinearNewtonAfterIterations",
             "Nonlinear System",
             ""
@@ -75,8 +75,8 @@ class Proxy(linear.Proxy):
             )
         )
 
-        obj.NonlinearIterations = 500
-        obj.NonlinearNewtonAfterIterations = 3
+        obj.NonlinearIterations = (500, 1, int(1e6), 50)
+        obj.NonlinearNewtonAfterIterations = (3, 1, 100, 1)
         # for small numbers we must set an expression because we don't have a UI,
         # the user has to view and edit the tolerance via the property editor and
         # this does not yet allow to view and edit small numbers in scientific notation