- minor documentation fixes.

- drush_pm.module: Added a command to refresh the update status cache.\n- code style issues resolved

Initial commit of the new drush.module ('The Drupal Shell') for Drupal 5 featuring a new command-line API, several tools and the 'Drush Packet Manager' to install and update modules from the command line.

Implemented the drush_op() wrapper for catching all mutative, destructive and external operations, allowing them to be suppressed (when running in simulation mode) and recorded.

Imported cache.drush, which provides built-in actions for displaying and managing the Drupal page cache.

Show friendly column headers in text tables when running in verbose mode; initial implementation of CVS update helper.

Imported watchdog.drush, which provides built-in commands for viewing and managing the Drupal watchdog log.

Implemented exhaustive depth-first search for Drupal root directory and added explicit -r option to specify it.