Initial commit in Index project

Added Core reference
Adding PetaPoco package.
Adding SQLite Data Provider.
Adding DB models.
Adding repositories.
Adding 'idf' field to Terms model and 'tf' to TermDocument relationship.
Merge branch 'develop' of https://github.com/renehernandez/InfoRecovery into feature/index
Restructuring models and repositories.
Changing 'IRepository'
Changing data representations.

- Removing 'Term', 'Document', 'TermDocument' model.
- Removing 'TermRepository', 'DocumentRepository'.
- Adding 'JsonStorage' model.
- Adding 'JsonStorageRepository'.
Changing 'DataManager'.

Using new data representations (JsonStorage).
Prove of concept.
Merge branch 'develop' into feature/index
Adding console application functionalities.
Merge branch 'develop' into feature/index
Storing and retrieving Json formats in DB.