WIP: Port pm to Annotated

[jonhattan]

Here's a starting point to work on pm commands.

I've build a quick&dirty code generation tool to start up with the boring part of commands conversion - https://github.com/jonhattan/drush-convert-commands

Incomplete list of next things to do:

• Add validation and other hooks
• Stop using drush_get_option()
• Figure out how to use engines
• Figure out how to declare suboptions
• Extract utility code from pm.drush.inc (drush_get_projects(), _drush_pm_find_common_path(), drush_pm_enable_find_project_from_extension())
• Remove Drupal 7 compatibility

[weitzman]

Decided to restart this as a by-hand port. See #2640