Add new regression tests

Refactor PageAnnotationImportSystemTest

- Rename PageWithTemplateInclusionRegressionTest
- Add DatePropertyRegressionTest
- Add MwImporter to handle only the imported tasks
- Add MwImporterTestBase which encapsulate import and
setup tasks

Integration is covered by:
- MwImporterTestBase
- PageWithTemplateInclusionRegressionTest
- WikiPage
- WikitextContent
- Parser
- Preprocessor_DOM
- SMW\Setup
- SMW\ShowParserFunction
- SMW\AskParserFunction
- SMW_QueryProcessor
- SMW\ResultPrinter
- SMW\ListResultPrinter
- SMW_ResultArray
- SQLStore\SMW_SQLStore3
- SQLStore\SMW_SQLStore3_Readers
- SMW\MediaWiki\Database