Ignore more auto-generated files in src/ tree
Move cern.libmadx.resource to cern.resource

In fact the code in this folder is largely independent of Mad-X, so it
could be distributed in a completely separate package.
Put files in src/cern/resource under quasi-public domain

As these files may be useful in other applications it is convenient to
have them under public domain.
Add license notice to src/cern/cpymad/model_locator.py

Licensed as Apache 2.0 like the rest of the project.
Delete only extracted files in resource.package.PackageResource.filename

Packages may be filesystem or zip. For zipped packages the filename()
method should extract the file and delete it after usage. For filesystem
the resource file, however, the resource file must never be deleted.
Migrate cpymad to new ModelLocator/ResourceProvider architecture

Start using the cpymad.model_locator as model loader in cpymad.service
and cpymad.model.