point_class call in Model.load() is not keyworded

[laelnasan]

Just a simple issue that prevents me to reuse the code with a new class which inherits Point. I can make a pull request to correct it if possible.

At sunspec.core.device.Model.load, line 709:
now:

point = point_class(block, point_type, str(point_addr))

what I'ld like:

point = point_class(block=block, point_type=point_type, addr=str(point_addr))

[altendky]

When you inherit your constructor should be compatible anyways what with super() calls and not actually knowing which constructor it will hit next in the MRO. But I personally do pass named arguments almost always anyways so the change itself seems reasonable.