Add some comments on loggin
Sample implementation of sample hierarchy strategy

A lifecycle callback allows for the population of null relationships to
a parent at load time. A new web resource demonstrates how to create new
null relationships.
Experiment with REQUIRED
Added a method to delete rows from the sample_hierarchy table with a null parent_id and renamed createSelectNullParentCountQuery method to selectNullParentCountQuery
Merge pull request #230 from SeqWare/feature/seqware-1916_experiment

Feature/seqware 1916 experiment