Deactivate bad unused import.

* ebaysdk missing from project requirements.
Enable pylint imports check (F0401).
Do not pylint inside html/bower_components.
Subpackage db and test folders.

* Effectively allows relative imports from/to these folders.
Fix broken imports in the db, features and test packages.
Locally disable import errors.

* Unable to import distutils.utils in Travis CI.
Merge pull request #665 from Renelvon/sane_imports

Install package structure. Fix imports (part 1). Enable pylint flag F0401.