Use PhutilArgumentParser in Daemon overseer/executor

Summary:

• Add a 'repeatable' flag for argument specifications.
• Add some code to detect and throw on invalid specs (e.g., parameter +

wildcard).

• Fix a bug where 'help' would show param name twice even for arguments with

no short flag.

• Rename 'printHelp()' to 'renderHelp()'.
• Add 'printHelpAndExit()'.
• Convert launch_daemon.php to use PhutilArgumentParser.
• Convert exec_daemon.php to use PhutilArgumentParser.

Test Plan:

• Ran unit tests.
• Ran daemons directly (launch_daemon.php, exec_daemon.php) and via "phd" (phd

debug, phd launch, phd status, phd stop).

• Ran utf8.php.

Reviewers: davidreuss, btrahan

Reviewed By: btrahan

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D1537