Port Largo code over exactly

[benlk]

• As part of this, open a pull request in Largo that contains the version of Largo with Disclaimers removed.
  • disclaimer_enabled is the option to search for
• don't port the option-page option to enable/disable it, because that is now controlled by installing/uninstalling the plugin.
• do port the option-page option to set the sitewide setting
  • create a plugin-wide options page
  • De-Largo Largo code #3

Changes to make in Largo

• create a function on the upgrade hook in Largo/inc/updates.php that migrates the Largo-style optionsframework option to a standard WordPress Option
• Remove Disclaimers functionality from Largo WPBuddy/largo#1500

[benlk]

Note that https://github.com/INN/largo/blob/v0.5.5.4/tests/inc/widgets/test-disclaimer-widget.php is not ported, as it solely exists to make sure that the Largo option for toggling the disclaimer widget's functionality actually toggles that functionality. In this plugin, the functionality-toggling functionality is toggled by activating or deactivating the plugin.

[benlk]

The corresponding Largo pull request is WPBuddy/largo#1501.