Expression & Predicate, variardic formatting
Element::define(), schema-definition.php
Columns defined in schema-elements.php, removed individual classes
Expressions defined in query-elements.php
Non-static aliasing so tests can run without backupStaticAttributes
query\ColumnRef, query\TableRef
Namespace expression\ split into core\, core\schema, and core\query
directory expression/ split up to match core/
Built basic relationship system

Currently supports OneToMany, ManyToOne, and OneToOne relationships.
Still need to build in support for ManyToMany