Fix TomcatServerSimpleIntegrationTest.teraDown
    
- so stops management context
Fix AbstractWebAppFixtureIntegrationTest
    
- use of persister for serialising: use multi-file rather than
  in-memory
Deprecate BrooklynMementoPersisterInMemory

- and BrooklynMementoPersisterToFile
Add RebindTestUtils.checkMementoSerializable(memento)