Changed plugin configuration table

Configuration of the plugin is now stored in table 'config_plugins' (where it belongs).

	modified:   backup/moodle2/backup_etherpadlite_stepslib.php
	modified:   backup/moodle2/restore_etherpadlite_stepslib.php
	modified:   db/upgrade.php
	modified:   etherpad-lite-client.php
	modified:   lib.php
	modified:   mod_form.php
	modified:   settings.php
	modified:   version.php
	modified:   view.php