So this allows people to alter the APIs for their plugins and allows
plugins to verify the API is compatible with the one they expect.
It adds a version property to Plugin classes, and has a SemVer checking
method which can be called from other plugins to verify a plugin against
a particular version.
Relented on the strict import of direct objects/classes for the typing
module only. Typing module components can be directly imported because
it makes the code really painful to read and write otherwise.
This is still in-line with the python style guide adopted from Google at
http://google.github.io/styleguide/pyguide.html section 2.2.
We determine address_masks using log/ln2, which cannot accept 0.
Therefore we don't support address spaces with a maximum_address of 0.
This can affect registry hives, so we've added a check in registry hives
to prevent creating layers with invalid maximum_addresses.
By not passing the arguments from exceptions down to the
base class Exception, it causes an issue when they are
pickled to be passed between processes. For more information,
see http://bugs.python.org/issue1692335.
Mike Auty