When load() was called in checkConsistency where namespace_dict was not given
and thus equal to the default function parameter value, exec would set the
function namespace_dict parameter, thus the next call would have
namespace_dict already set when it was given.

This fixes testInvalidSourceCode when being ran for TestZodbExtensionComponent
and TestZodbDocumentComponent in the same runUnitTest.

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.