Revert 4b16e1d and 75618d4.

This reverts commit "use UnrestrictedMethod's super user instead of ad-hoc
SUPER_USER." and related commits.

This commit breaks Python Script installation through UnrestrictedMethod (for
example upgrader Alarms for bt5s), thus the Owner of Python Scripts will be
'System Process' (erp5/acl_users). However, Zope checks Owner when executing
Python Script which fails because 'System Process' cannot be found in
erp5/acl_users.

Legacy SUPER_USER was working through a virtual user as implemented in
enumerateUsers (ERP5Security.ERP5UserManager).

Conflicts:
	product/CMFActivity/ActivityTool.py
	bt5/erp5_user_tutorial_ui_test/SkinTemplateItem/portal_skins/erp5_user_tutorial_ui_test/Zuite_checkPortalCatalog.xml