Update documentation.
Add documentation. Strict check.
More documentation.
Document DboSource::getConstraint().

Also, update the function signature (to be compliant with other
functions) and type hint $LinkModel.
Still more documentation.
Merge pull request #2519 from bar/2.5-dbosource

Update documentation.
Merge pull request #2518 from bar/2.5-dbosource-getconstraint

Document DboSource::getConstraint().
Be more semantic indicating that association fields must be empty.
Get Model associations only when needed.
Conveniently fetch hasAndBelongsToMany associations from within a function (like hasMany).
Variable names should represent their values.
Remove unnecessary references.
Be more semantic with variable names.
Isue less loockups for deep arrays.
A bit of documentation added.
Avoid recalculating whether the relationship is a self join.
Process query only when needed.
Be consistent with the result set variable name.
Re-expose DboSource::fetchAssociated() for BC.

Internally use protected methods to fetch hasMany and hasAndBelongsToMany
associations.