Add brush import/export test, add test files
Before this commit there was no brush import/export tests
at all, this commit adds permissions tests and incorrect
This commit also adds tests files. They would be generated during the
test run but only if "data" directory already exists, which is not that
obvious since some of the tests didn't have any test files and you can't
push empty directories to git, hence addition of all files.
Their permissions (for permissions tests) will be set correctly
in the test itself anyway.