add a test for char options
add support for char types to the lexical cast, to allow single character types that make sense, add a integral_conversion operations to simplify the conversions from string to integers and allow discrimination in a few cases with enumerations.
* Update options.md book chapter and the readme to better reflect current usage and the modifications to the add_options templates.
add support in add_option for wrapper types, such as std::optional, boost::optional or other types with a value_type trait. Add support for generalized containers beyond vector, add support for nested tuples and vectors, and complex numbers directly in add_option. This includes several new type traits and object categories.
Upgrade the google test version to better support templated tests.
add support for vector argument separator `%%`
* update formatting to match recent changes
* Apply suggestions from code review
Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
