[server/test] do not depend on third party cubes Drop requirement of basket, card, comment, file, localperms and tag cubes for cubicweb.server tests. Copy needed part of schema, entities, views, hooks into the cubicweb/server/test/data directory (which is included in PYTHONPATH for CubicWebTC tests). For migration tests which use different "datapath", use symlinks to have dependent cubes importables.