AtlCoolConsole: Rely on python's normpath module to make the cd command more functional

COOL folders and foldersets have some similarity with files and directories of file-systems. The AtlCoolConsole mimics the shell-commands cd and pwd to navigate the folder structure.

I was always a bit annoyed by the limitations of the cd command of the console. Luckily, python's posixpath.normpath module does exactly the string manipulations we need to make the cd command of AtlCoolConsole bash-like.