Db context extensions.o space

Same as 
https://trackable.codeplex.com/SourceControl/network/forks/azabluda/TrackableEntitiesContrib/contribution/7246

> My proposal for https://trackable.codeplex.com/workitem/36

> Given no failing unit test for the described problem, I would simply suggest to consider this PR as a general code cleanup. I hope it doesn't break any other test (quickly checked it with my local connection string). As a side effect, it is very likely to fix the "same name in different namespaces" problem.