Prevent possibility to edit "new participant"

[Elblinator]

Current behaviour:
If an admin adds an account to a meeting and changes the personal information (without having the right to do so) then the following Error is thrown and the account is not added as participant:

Error: You are not allowed to perform action user.update. Missing permissions: OrganizationManagementLevel can_manage_users in organization 1 or CommitteeManagementLevel can_manage in committee 10 or Permission user.can_manage in meeting 56

Recreation:

1. create an admin (not super-/orga-/accountadmin) who is only admin in one meeting (meeting A)
2. create a participant (C) in meeting B
3. With the admin in meeting A try to add C (select C in step 2)
4. go to step 3 and change your present status from present to not present to present
5. and change/add some information
6. press save
7. the error is thrown

if you were not able to change/add any information in 4. then do not add C and reload the participant-list and try again

Wanted behaviour:
a normal admin should not be allowed to change any information from an already existing account, except if the admin is an admin in ALL meetings from this account.
The personal information-fields of such accounts should be disabled

What the add page most of the time looks like:

(edited after revelation that the bug needs an autoupdate to make changes possible, for the whole discussion see #2815 )