Delete History per dsrini-open

Add on provides options to delete history items or skip the deletion (when clearing all history) by a website host or domain configuration.

Additional configurations allows users to clear history for configured sites when one closes the browser window.

Configuring the add-on with the ignore list and/or the delete list enables the appropriate popup menu options as well. Users are enabled to delete history for the current website or for the configured delete list.

All configuration options are synced with Firefox sync.

Provide feedback or suggestions for improvement including any issues in the github project page.