This patch updates the last user of ArgInfo::count and deletes
it. I also delete GetNumInitArguments() and GetInitArgInfo().
Classess are callables and GetArgInfo() should work on them.
On python 3 it already works, of course. inspect is good.
On python 2 we have to add yet another special case. But hey if
python 2 wasn't crufty we wouln't need python 3.
I also delete is_bound_method becuase it is unused.
This path is tested in TestStepScripted.py