Implement Match / Switch / Case Flow Keyword

Implementing this will require a bit of studying of the existing FlowLogic methods. Shouldn't be too hard though. The hardest part should be determining the syntax that we want to go with.

match $(getconf LONG_BIT)
    case "32"
        echo "32-bit OS found"
        end
    case "64"
        echo "64-bit OS found"
        end
    case _
        echo "Unsupported OS architecture"
        end
end

We could introduce two new statement types: Match and MatchArm. The statement splitter should be able to split upon detecting a complete match arm.