removed TODO
refactored PathArgValidator to throw PluginErrorException instead of reporting errors via Sandbox
style fixes in FileFunction
added Path.firstElement()
simplified error handling code in FileFunction
FileFunction forbids paths to smooth directory
style fixes in FilesFunction
FilesFunction forbids paths to smooth directory
simplified error handling code in FilesFunction
FilesFunction forbids paths equals to root dir
simplified error handling code in SaveFunction
SaveFunction forbids dir path pointing to smooth directory
refactored SaveFunction
added TODO