Fixes composer-installer v4 Errors

[BUGFIX] Don't start a request for external content elements if they have specified the source in a data attribute

[BUGFIX] Cleanup, Fix broken external-contnet-no-protection frame class, Fix broken external content frame class

[BUGFIX] Do not save UUID unless the statistics have been activated and the user has saved any preferences. Also add essential cookie explanations for uuid and last preferences.