Only consider .py and .xml files when importing BusinessTemplate files in FilesystemToZodbTemplateItem.

This fixes tests failures with ``AttributeError: 'str' object has no attribute
'text_content''' due to .pyc files.

Fix hasErrorMessageList() of ZODB Component as error_message (component_validation_workflow variable) is always set.

Modules to be handled by the Component import hook must have already been
filtered properly in find_module().

Add ZODB Document BusinessTemplate tests as expected failure for Constraint and Test (not implemented yet).

This fixes filesystem Document-related tests in testBusinessTemplate.

Otherwise, following ZODB Document tests will fail because of the ZODB
Document created but not removed in that test.

Before, ConsistencyMessage were stored into a separate workflow variable,
instead of using error_message workflow variable which contains instances of
Message.

The only purpose of having Interaction Workflow defined on ComponentTool
_setObject and _delObject was for BusinessTemplate installation and
uninstallation, however the reset was also triggered when a new draft
Component was being added. Instead, perform the reset in BusinessTemplate
DocumentTemplateItem.