Default tests and models for new users

[ddelpiano]

• When a new user is create we need to create / clone sample test and sample model instances (2 per both but we can start with one meanwhile Rick will provide the second couple) for the user just created.
• We might want to create a demo user that will own the 2 tests and 2 models that we will clone everytime we create a new user (open for discussion if a better solution can be implemented).

List of tests:

• InputResistanceTest (neuronunit.tests.passive)
• second test to be provided by @rgerkin

List of models:

• LEMS_2007 (ReducedModel)
• second model to be provided by @rgerkin