New settings check against valid options

[ngoiz]

Introduces a small new feature to check that settings are valid and also adds valid options to the relevant settings' documentation.

The same way we have settings_types, settings_default etc, we now have the dictionary settings_options for those settings that are either int, str or list(str) that have certain possible options. The entry for each setting in settings_options is a list.

Example:
The convection scheme in StepUvlm is an int that can be 0, 2 or 3. The new dictionary would have an entry like:
settings_options['convection_scheme'] = [0, 2, 3]

To implement this feature to your code:

• Documentation table:
  __doc__ += settings_table.generate(settings_types, settings_default, settings_description, settings_options)
• Settings to custom settings:

  settings.to_custom_types(self.settings,
                               self.settings_types,
                               self.settings_default,
                               self.settings_options)
  

This will check the settings and raise an error if the desired option is not valid. In the case of a string, it will always accept the empty string as valid without need of adding an empty string to the list of valid options.

This is totally backwards compatible and does not need any modification unless you would like to implement these settings check.