Incorrect behavior with "Form submissions" while copying the plugin.

[vstoykov]

If the plugin is copied the original reference to the Form instance is preserved and it's name is replaced with the name of the new "form". This way there are more than one FormDefinitions which point to the same Form. In the administration in "Form submissions" submissions from all of these forms are combined under one "Form" which has the name of the last FormDefinition saved. This is kind of confusing.

The problem probably lies in the logic of PluginReferenceField.pre_save. Further investigation is needed.