[test] Replace symlinks in legacy_cubes by real copies
This solves a "python setup.py build" issue on my machine.
Copying these files should not be a big deal because they
have been dropped in the "default" branch and we would not
touch them in 3.26 branch.
3.26 (1 February 2018)
======================
New features
------------
* For ``pyramid`` instance configuration kind, logging is not handled anymore
by CubicWeb but should be configured through ``development.ini`` file
following https://docs.pylonsproject.org/projects/pyramid/en/latest/narr/logging.html.
Backwards incompatible changes
------------------------------
* CubicWebConfiguration method 'shared_dir' got dropped.