Enhancement: Added support for applying additional join conditions for
"get_sub_entries()"
Enhancement: Added support for excluding or only loading DataLinker
children of a given identity in "get_sub_entries()" and
"get_sub_entries_count()"
Enhancement: Added support to define a default instance specific sort
order applied when loading a relationship
Enhancement: Added support for context specific logging
Trivial: Used column sort notation of SQLAlchemy for better readability
Trivial: Restructured module header