feat (Column.php) add column container
feat (Constraint.php) add constraint container
feat (Model.php) add model class to incapsulate manipulation logic
feat (Relation.php) add table container
fix (Constraint.php) remove inheritance
feat (Relation.php) add addColumn()
feat (Model.php) implement getColumns()
fix (Model.php) import class list
feat (Relation.php) add addConstraint()
feat (Constraint.php) add addColumn() and type constants
feat (ConstraintColumn.php) new container
feat (Model.php) add getConstraintColumns()
fix (Model.php) return value in all methods
docs (Model.php) fix phpdocs return types
feat (Column.php)) new $comment property
feat (Model.php)) change sql to fetch comments for columns
feat (Model.php) look up table in database before creating object
feat (Relation.php) new fields $comment, $rowCount, $tableSpace, $status
fix (Model.php) throw error if no such table exists
feat (Relation.php) add getters for new fields