By using AppSettings::AllowLeadingHyphen values starting with a
leading hyphen (such as a negative number) are supported. This
setting should be used with caution as it silences certain
circumstances which would otherwise be an error (like forgetting
a value to an option argument).
Closes#385
This commit adds support for values separated by commas such as
--option=val1,val2,val3. It also includes support for uses
without the equals and shorts (both with and without)
--option=val1,val2
--option val1,val2
-oval1,val2
-o=val1,val2
-o val1,val2
Closes#348
