db: remove first migration for creating sources
.gitignore: ignore database configuration file
test: update folder structure to new rails 4 naming convention

In Rails 4 the folder test/unit has been renamed to test/models and
the folder test/functional has been renamed to test/controllers.

While the present structure works it is best to change to the new
structure since newly generated test files are put into the new folders.
refactor: move backends from controllers to models

The backend classes are more resembling of models than of controllers.

One can view the backends as a model which lives on the Internet instead of
inside the database.
backend: add missing id and properly parse duration

Fix two bugs in the YouTube backend:
 * Add 'id' as a requested part when fetching details
 * Add missing hash field when parsing video duration
refactor: use blank? and present? to make code prettier