- 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