Do not allow specimen tube registration to select a different laterality than what already exists

[Nicklas Nordborg]

There is a use case when a SpecimenCoreBiopsy for a case already exists in the database. When registering a second Specimen (surgery) the laterality from the core biopsy is selected by default. The user is still allowed to change to another laterality (or none). A warning message is displayed but the registration can proceed. The end result is that a Specimen item is created an linked to a Case item but the laterality may not match. This confuses the other wizards which expect that child items to a case always have the same laterality as the case.

See also #491, which prevents the referral form registration from fixing this issue.

[Nicklas Nordborg]

(In [1980]) Fixes #492: Do not allow specimen tube registration to select a different laterality than what already exists