Streamline Fabric CLI interface

[traut]

Fabric CLI:

• 2 subcommands:
  • render
    • the subcommand renders the specified document into Markdown and outputs it either to stdout or to a file.
    • target -- a required positional argument. Specifies the name of the document to be rendered as document.<name>.
    • --out-file -- an optional argument. Specifies the name of the output file where the rendered document must be saved to.
      • if --out-file is not set, the Markdown is printed to stdout
  • data

    • the subcommand executes the data block and prints out prettified (and highlighted) JSON to stdout

    • target -- a required positional argument. Specifies a path to a data block to be executed -- a data block must be inside a document, so the path should have syntax of document.<doc-name>.data.<plugin-name>.<data-name>.

• subcommand-independent arguments
  • --source-dir -- an optional argument that accepts a path to a directory with *.fabric files. Default value: . (current directory)
  • --log-output -- an optional argument that accepts plain or json. Configures a handler for the logging. Default value: plain (colored plain text output). The logs (both plain and json formats) should be written to stderr
  • --logging-level -- an optional argument that specifies the logging level. Default value: info
  • -v -- a shortcut to --logging-level debug

[traut]

based on the #58 (comment), decided to rename --logging-level to --log-level for clarity