fix create_user function introduced in d6ae30c5d055 for database initialization: messup admin user groups when anon is created due to missing restriction

3.6 api update

fix unittest_hooks: attributes have now update_permission instead of [add/delete]_permission

when modifying a persistent schema, erschema may miss some permissions which wil trigger a key error, but we don't want to crash on such cases

fix #694445: related entity generates weird RQL which in turn generates weird SQL which fails on SQL Server quick fix to reuse modification_date if already retreived by the rql query.

fix 4626:c26b4df9fc90 (#703911): use can't rely on peid since it's not an actual eid when we're creating the parent entity

[form fields] nicer behaviour of the password field: don't put internal field value on edition (triggering validation error if one validation without removing the value, due to confirmation mismatch), and don't show the field as required in such case