#5 SUBNET_PARAM should not be considered as a parameter type

[Carle Cote]

Using SUBNET_PARAM as a type can lead to
inconsistencies. Type should be defined at the Node
level and propagate to network level. Actually, it is
possible to define a parameter type at network level
which means that the parameter type of a specific Node
can be different according to the Network using it.
Exception is now occurs if type defined at Network
level does'nt correpond to what is expected at the Node
level. This can be avoid by considering SUBNET_PARAM as
an option of a Node parameter instead of a type.