prototype cabal new-clean command

cleanAction :: CleanFlags -> [String] -> GlobalFlags -> IO ()
cleanAction cleanFlags extraArgs globalFlags = do

    projectRootDir <- findProjectRoot
    let DistDirLayout{distDirectory} = defaultDistDirLayout projectRootDir

    notice verbosity "cleaning..."

    -- Remove the whole shared dist dir
    chattyTry "removing dist/" $ do
      exists <- doesDirectoryExist distDirectory
      when exists (removeDirectoryRecursive distDirectory)

    -- Any extra files the user wants to remove
    mapM_ removeFileOrDirectory (extraTmpFiles pkg_descr)

    unless saveConfig $ do
      -- Delete the cabal.project.local too
      
  where
    verbosity  = fromFlagOrDefault normal (cleanVerbosity cleanFlags)
    saveConfig = fromFlagOrDefault False  (cleanSaveConf cleanFlags)