rave: Make file system errors inherit from proper io.* base classes.
rave: Update filesystem bad path pattern to remove earlier false-positives.
rave: Copy file cache while transforming due possible modifications.
rave: Properly process provider local paths in file system.
rave: Implement FileSystem.list() for subdirectories.
rave: Fix-up typo in file system when mounting a provider.
rave: Raise filesystem.NotAFile when trying to open a directory.
rave: Return an empty string for basedir("/") instead of None for API compatibility.
rave: Fix FileSystem.seek() to be API-compatible with native file.seek().
rave: Add API to set the global log level.
rave: Fix-up broken English in rave.modularity internal APIs.
tests: Add basic directory structure.
tests: Add file system tests.