Allow lists/tuples of tensors to get tagged as application inputs

[dwf]

Related to #1139 (which is my workaround to this issue for the time being), I'm in a situation where I have multiple, paired sets of inputs to an application but not necessarily a fixed number. It'd be nice if list and tuple arguments to an application method that contain tensors could have their contents sensibly tagged.

What I'm doing in my own code right now (I'm passing all my apply arguments via **kwargs here):

        _annotate = partial(copy_and_tag, brick=self,
                            call=application_call,
                            role=INPUT,
                            application_name=application_call.application.name)
        for kw, value in kwargs.items():
            if isinstance(value, (list, tuple)):
                kwargs[kw] = [_annotate(v, name='{}[{}]'.format(kw, i))
                              for i, v in enumerate(value)]

[dwf]

I think the cleanest thing is probably to just do an isinstance check on the variable argument in copy_and_tag recurse if a list or tuple is found. We could also make this behaviour configurable in the Application constructor as pass it as an argument to copy_and_tag.

[dwf]

(Actually, type(variable) in (list, tuple) would be safer since we know how to actually construct those objects, but not necessarily for subclasses; we could just assume that type(variable)(<sequence>) is the right constructor but this is dangerous.)