Prefix ParseResult methods with `matched` if they return only matched options/positionals

[remkop]

Currently methods are named

• options
• positionals
• option(char), option(String)
• positional(int)
• hasOption(char), hasOption(String), hasOption(OptionSpec)
• hasPositional(int), hasPositional(PositionalParamSpec)

These should all be prefixed with matched, so matchedOptions, hasMatchedOption etc.
This helps to clarify the semantics of #340 and #341 .