ERP5.Document.BusinessTemplate: Support object type changing from container to non-container.

For example, allows upgrading a Business Template when an ERP5 Form is
replaced by a PythonScript in a skin folder.
7 jobs for for_testrunner_3 in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-Master

00:41:55

passed ERP5.PerformanceTest-Master

00:22:50

failed ERP5.UnitTest-Master

04:32:24

failed ERP5.UnitTest-Master.Medusa

04:34:31

passed ERP5.UnitTest-TestRunner3

01:15:31

passed SlapOS.Eggs.UnitTest-Master.Python2

00:17:02

passed SlapOS.Eggs.UnitTest-Master.Python3

00:13:17