Wic plugin machinery implemented using metaclasses.
Reimplemented plugin machinery using this advice from
https://wiki.python.org/moin/PortingToPy3k/BilingualQuickRef
Syntax for creating instances with different metaclasses is very
different between Python 2 and 3. Use the ability to call type instances
as a way to portably create such instances.
Now it should work under both Python 2 and Python 3.
[YOCTO #9412]
Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
