[Examples] Fix deprecation warning.
[API] Massive code reorganization.

Large amount of code have been migrated to the detail/* section.
[Code Style] Wording and style.
[Code Style] And again.
[Code Style] Style review for string formatting functions.
[Unit Testing] Cleaning up.
[Aux] Drop unused constructor for join iterator.
[Unit Testing] Refactoring.
[Code Style] Extracting implementation part for attribute set view.
[Unit Testing] Several tests.
[Unit Testing] Testing record's default constructor. One task less.
[Unit Testing] Record is now completely tested.
[Documentation] Added documentation about exception raised from attribute extracting method.