New eForms subtype required

[csnyulas]

Starting with eForms SDK v1.12 there is a new eForms subtype E6:
https://docs.ted.europa.eu/eforms/1.12/reference/code-lists/notice-subtype.html
(which was not present in SDK 1.11)

So, to allow a complete mapping of the values of field OPP-070-notice, we need a new subclass of epo-not:eFormsNotice, called epo-not:NoticeE6

This new class should appear in future version of this diagram:
https://docs.ted.europa.eu/EPO/latest/_attachments/html_reports/eNotice/index.html?goto=2:1:141

BTW, I am not sure why the epo-not:NoticeX01 and epo-not:NoticeX02 are not present in ePO, but once we will start mapping those notices as well, we will need those two classes as well.

[muricna]

X01 and X02 are not required they are not procurement specific notices.