This reverts merge request !16

Cleared up issues with Singleton behavior, largely confused by the fact this python logger itself is a Singleton that persists between tests

Mocked up session logging implementation using python log service; two tests are failing apparently due to Session singleton-related issues

Validated non-duplication when loading ilastik model with same project file name, irrespective of path formatting

Test covers problem with models being duplicated because of different path specifications; not yet fixed at API level