Some general improvements

This Pull Request makes several improvements.
* The delete page in the User CP is now served from the da_delete_account template (in the global templates set).
* Improved the deleted_users table
	* The deleted_users table is created from the users table meaning any new columns are immediately added.
	* The deleted_users table stays up-to-date with changes to the users table by checking for new columns when a user is deleted.
* Stops the language file from being loaded multiple times.
* Only loads globals if and when they are needed.
* Avoids administrators accidently uninstalling the plugin and losing the deleted users and is unable to restore them.
* Stops an errors on install by removing gid and changing is default to an integer.
* Logs the IP a user is deleted from and displays in the table in the Admin CP.
* Improves inconsistencies of the table headings (some ended with colons and some didn't).
* Improved code readability.