This cleans up the type checking a bit and makes it more readable, along with some other cleanup.
* start work on trying to clean up the type traits for which lexical cast overload to use
* fix readme issue and make the condition tests a little clearer
* add a check for out of range errors on boolean conversions
* Fix capitalization and some comments on option functions
* fix a few code analysis warnings for VS2019
add some test of the remove_excludes functions
add test for Issue #256
add remove_subcommand fail test
add remove_subcommand function and add_subcommand to option_group and some tests associated with them.
Allow option groups to use ignore_case ignore_underscore for inheritance
Allow option groups to specify allow_extras even if the parent app doesn't in which case extra options flow down into the option_group.
rework return values from _parse_* function to return true if the value was processed false otherwise, this simplified the logic and got rid of the pulling and clearing of the missing fields from option groups.
add TriggerOff and TriggerOn helper functions and some tests for them
add shapes example of multiple callbacks in order.
allow specification of callbacks that get executed immediately on completion of parsing of subcommand
add tests for enabled/disabled by default
add _get_fallthrough_parent. To get the most appropriate parent to fallthrough to
add enabled and disabled by default functions
add positional_arity example
Add a pre_parse_callback_ for apps. The Pre parse callback takes an argument for the number of remaining arguments left to process, and will execute prior to parsing for subcommands, and after the first option parse for option_groups.
* change the move function to _move_option and add an additional test
add a validation check on min options to make sure it is even possible to succeed.
add some additional tests to cover code paths and potential errors.
add a number of additional tests and checks and fix some issues with the add function in option_groups
clean up example and help formatting
add option_groups example to play with
move create_option_group to a member function using a dummy template
add some optionGroup tests
add min and max options calls and an associated Error call
* add ranges example, add excludes to app for options and subcommands.
* add some tests on ranges, and some subcommand tests with exclusion
* add tests in optionGroups for some invalid inputs
* add required option to subcommands and option_groups
* add disabled flag
* add disable option to subcommands and some more tests
* start work on ReadMe modifications
* update the readme with descriptions of function and methods added for option_groups
* clear up gcc 4.7 warnings
* some update to the Readme and a few more warnings fixed
* Minor readme touchup
