Feature/command line switches

Initial support for proper command-line parsing and switches :)

- Re-uses Phix's CliEngine (which has built-in command-line parsing, version and help support)
- Storyplayer's main loop now runs out of the PlayStoriesCommand class
- The test environment is now the -e switch
- No need to specify a test environment if only one environment defined in the config files
- Added new 'list-environments' command to show list of all defined test environments
- Tied up Static and Runtime config code, and moved it out of PlayerLib into new Cli namespace
- Added $st->saveRuntimeConfig() for use in Prose modules (to avoid modules having to know which config manager to use)