CLI help options too crowded

[phackstock]

When using the CLI and consulting the --help option for nomenclature validate-project, I noticed that the output is currently a little crowded:

nomenclature validate-project --help
Usage: nomenclature validate-project [OPTIONS] PATH

  Assert that `path` is a valid project nomenclature

  Parameters ---------- path : Path     Project directory to be validated
  definitions : str, optional     Name of the definitions folder, defaults to
  "definitions" mappings : str, optional     Name of the mappings folder,
  defaults to "mappings" (if this folder exists) dimensions : List[str],
  optional     Dimensions to be checked, defaults to all sub-folders of
  `definitions`

  Example ------- $ nomenclature validate-project .
  --definitions <def-folder> --mappings <map-folder>
  --dimensions "['<folder1>', '<folder2>', '<folder3>']"

  Note ---- This test includes three steps:

  1. Test that all yaml files in `definitions/` and `mappings/` can be
  correctly read    as yaml files. This is a formal check for yaml syntax
  only. 2. Test that all files in `definitions/` can be correctly parsed as a
  :class:`DataStructureDefinition` object comprised of individual codelists.
  3. Test that all model mappings in `mappings/` can be correctly parsed as a
  :class:`RegionProcessor` object. This includes a check that all regions
  mentioned    in a model mapping are defined in the region codelist.

Options:
  --definitions TEXT  Optional name for definitions folder
  --mappings TEXT     Optional name for mappings folder
  --dimensions TEXT   Optional list of dimensions
  --help              Show this message and exit.

It seems that click is mashing up multiple doc strings.
Should be easy enough to clear that up.