global options table.
Every Command instance now has its own copies of the global options,
  which automatically fallback to the Distribution instance.  Changes:
  - initialize them in constructor
  - added '__getattr__()' to handle the fallback logic
  - changed every 'self.distribution.{verbose,dry_run}' in Command to
    'self.{verbose,dry_run}'.
  - filesystem utility methods ('copy_file()' et al) don't take 'update'
    parameter anymore -- instead we pass 'not force' to the underlying
    function as 'update'
Changed parsing of command line so that global options apply to all
  commands as well -- that's how (eg.) Command.verbose will be initialized.
Simplified 'make_file()' to use 'newer_group()' (from util module).
Deleted some cruft.
Some docstring tweaks.