Help text for Options::Auto<T> doesn't include T

[wthrowe]

It shows something like

  Options:
    Arg:
      type=Auto
      Help text

without indicating what type can be passed instead of "Auto" (or if the special string is "None").

The text displayed is governed by the yaml_type struct in OptionsDetails.hpp, which is overloaded for some standard library types but otherwise just uses pretty_type::short_name. Some way of overriding the name for user-defined types will need to be added.

It might be possible to merge this information into the create_from_yaml struct.