Create drush command to execute optimization

Problem/Motivation

Currently, the module always binds itself to the Drupal Cron. It will be good to provide a way to allow people to execute the optimization process manually without forcing a cron task.

Steps to reproduce

Proposed resolution

* Provide an option to disable cron execution, i.e. An option for "Never".
* Provide a Drush command, say, drush opdb

Remaining tasks

User interface changes

API changes

Data model changes