test-first implementation for paths
mlpaths, pathjoin, pathsplit tests and implementation
Fix: test_mlpaths suite failed accessing built-in path, because it's called matlabpath
Fix: test_pathjoin fails on Unix
Fix: pathsplit returns empty cell for string argument, but should return empty cell string
Fix: test_mlpaths fails on wrong assumptions. MATLAB's path returns the updated, addpath returns the previous path after setting.
Merge branch 'paths'