In PHP 8.2 and later, setting a value to an undeclared class property is
deprecated and emits a deprecation notice.
So we need to add missing class properties that still need to be declared.
Before applying a preset, the settings are displayed and, in some cases,
the Current/New value columns were empty.
This patch fixes it and guarantees this information is updated properly
every time the set_value() method is called.
This commit moves the presets subsystem to a location within the admin
folder, which is more appropriate given its purpose and reduces
developer frustration with tab completion of the admin directory.
Marina Glancy