Release: 0.6.0

• Added Clerk (in the new clerks module), a nagata.FileManager that is
  now the clerk of every Project and loader. It keeps data and results
  outside a project's code, in the "workspace" that holds the "code"
  folder: data in its "data" folder (or in a subfolder of it named by the
  new "data_subfolder" setting of the "files" section, such as
  "crime/nibrs"), and each run's results in its "studies" folder. The
  workspace is the folder that holds the nearest "code" folder above the
  current folder (or the current folder, if there is none), unless the
  AMOS_WORKSPACE environment variable or options._DEFAULT_ROOT names
  another. Before, a project kept its files in the current folder, so a
  project that relied on that should set "root_folder", "input_folder", or
  "output_folder" in its "files" section.