Updated code to comply with Drush standards - fixed deprecated function names, added callbacks to each defined Drush command

http://drupal.org/node/769316 - commit of Drush integration code provided by lambic (http://drupal.org/user/58843)

http://drupal.org/node/763786 - Added permissions filtering based on patch provided.  This means that supplied permissions to grant/revoke are validated against all defined permissions before granting or revoking.

Added new function (permissions_create_role()) for creating roles via the api.  This complements the permissions_get_role() function, which retrieves a role object by name.

- SQL error when inserting new permissions into the permissions table

- Added a function for retrieving all the permissions for a role and returning the results as an array
- Added a function for revoking all permissions defined in a module's hook_perm implementation
- Refactored all functions to use the permissions_get_permissions_for_role() function
- Updated the documentation in README

- Added permissions_grant_all_permissions() function, which grants all defined permissions to a given role
- Added permissions_grant_all_permissions_by_module() function, which grants all permissions defined by a given module to a given role