Utilities for creating Ruby command-line tools

This standardizes the following aspects of a command-line tool: - initializes the logging system (CmdUtil::Log), - setup OptParse with often used options (like --verbose/--debug/--help) - executes the run method within a catch-all exception handler

Changelog

• 1.0 - initial gem, CmdLine and LogMgr.
• 1.1 - better support of LogMgr in CmdLine (logger name from module)
• 1.2 - pass remaining arguments down to #run method
• 1.3 - improved --help output, new conventions for #add_own_options
• 1.4 - add show_help and show_version protected methods to CmdLine
• 1.5 - add create_optparse protected method to CmdLine
• 2.0 - Ruby 1.9 only, so use Logger
• 2.1 - output on console if possible unless --logfile given
• 3.0 - removed @log ivar; use ANSI::Logger when appropriate
• 3.1 - always log on $stderr unless --logfile is used
• 3.2 - add support for ANSI code via CmdUtil::ANSI::Mixin
• 3.3 - add CmdUtil#check_file utility method
• 3.4 - add log multiplexing (--logfile doesn't prevent console output)
• 4.0 - switch to Ruby 2.4 as baseline
• 4.1 - add CmdLine#main_status which contrary to #main does not exit
• 4.2 - dispense of win32console and support for verbosity/debug levels
• 5.0 - dispense of ansi module and new compact default output
• 5.1 - Loggable and color_logger!
• 5.2 - switch to Ruby 2.6 as baseline