Mappable objects and lists; Reorganization of the tests: now base tests defined in one project and inherited by others
Reached a mature state of the project:
- Operate by contract to repositories
- Type inferring for queries (filters)
- Object mapping by contract

Repository types:
- InMemory: a memory-based context (mostly for testing purposes)
- Entity Framework: data context around EF 6
- Dapper: An (incomplete) implementation of the context around Dapper
Fixes to object polymorphism support