Clean up Form Package

[dongilbert]

This PR cleans up the Form package to remove some CMS remnants.

• Remove JFactory from Form class.
• Remove JFactory from Rule\Email. Remove unique check, because it's for the CMS.
• Removing SQL field type. Create a custom field type instead.
• Remove Factory from Field\Timezone. Fix usage of JHtml.
• Remove unused tests.
• Remove ComboBox field type. Not used anywhere (not even in the CMS) and requires media.
• Remove password strength meter. Requires media.
• More cleanup

Thanks @mbabker for helping answer some questions on this. 👍

[dongilbert]

Doing a bit more work on this.

[dongilbert]

This latest PR removes all the add*Path and load*Type methods from the Form class that were just proxies to the identically named methods in FormHelper. I also moved around the UT's and created a test class for the FormHelper.