- Correct mispelling bug: Relationship.php: checkConditionValidity =>
  _checkConditionValidity.
Numerous changes:
- lib folder that contains actual library files.
- test folder that contains every files written to test the library.
- Add a Table class that handles table name, primary keys, table columns. Needed
  this to workaround a bad behaviour of static in PHP. (cf
  https://bugs.php.net/bug.php?id=49105)
- Save of linked models arborescence. (HasMany and BelongsTo are working).
Remove critical data