Support Drupal 7 in block commands. Also, provide a shortcut for block commands where arguments can be used in place of options in cases where doing so is unambiguous.

Restore drush_extras project with new commands.  Remove old commands which have moved to drush core.

New drush extras project. These are the usual commands, but no longer distributed with core drush. core drush is now well separated from drupal core and can even run against any verison of drupal, whereas these commands vary by major drupal version.