feat: class refactor

includes/class-base-settings.php

includes/class-integration.php

includes/class-menu.php

includes/class-settings.php

includes/fields/class-field.php

includes/fields/gf/iban/class-addon.php

includes/fields/gf/iban/class-field.php

includes/fields/gf/iban/class-gf-field.php

includes/fields/gf/index.php

includes/fields/index.php

includes/fields/wpcf7/iban/class-field.php

includes/fields/wpcf7/index.php

includes/fieldset-control-js.php

includes/integrations/gf/class-integration.php

includes/integrations/index.php

includes/integrations/wpcf7/class-integration.php

includes/options/index.php

wpct-erp-forms.php