Parameter: define create as a classmethod

[seb5g]

use class method to self define itself allowing the subclassing of Parameter object and creation of the subclass

My issue was that I had to reimplement getitem to override the default behaviour before calling super:

something like

class ParameterPatch(Parameter):

    def __getitem__(self, names: Union[str, tuple[str,]]):
        if names == 'multiaxes':
            names = 'controller'
        elif 'multiaxes' in names:
            names = list(names)
            names[names.index('multiaxes')] = 'controller'
            names = tuple(names)
        super().__getitem__(names)

but because Parameter are instanciated with the create method hardcoding the use of Parameter, it won't use the modified class. The current solution is to reimplement also the create method. The use of the classmethod decorator in this PR allow to not make this reimplementation

[j9ac9k]

Great change @seb5g !