Turning off the option for submitters to edit data disallows them from making an actual submission.

[ifokkema]

Describe the bug
LOVD contains a setting, "Enable submitters to change data?", meant to allow or disallow submitters to edit previously created submissions. However, turning that setting off actually makes it impossible for a submitter to create a submission since adding a screening to an individual is currently considered an edit. The submitter can, therefore, only create an individual when this setting is turned off.

To Reproduce
Steps to reproduce the behavior:

1. Login as manager or higher, go to the system settings, make sure that "Enable submitters to change data?" is off.
2. Log in as a submitter, and start a new submission.
3. After creating the individual, you are presented with an error that you need to have owner-level permission to continue.

Expected behavior
Submitters should be able to create a new submission with this setting off, add data to a previously created submission, but not edit any parts of that submission.

Your software (please complete the following information):
LOVD 3.0-29.

Additional information
lovd_isAuthorized() returns 0 when submitters aren't allowed to edit anything. 0 does not match false, so should be considered a success in this case.