* remove phase one/two distinction and hdbquery typeclass
* move extensions to default-extensions
* switch to LazyTx which only acquires a connection if needed
* move defns from TH module into Ops module
* remove tojson orphan instance for http exception
* remove orphan instance for dmlp1
* getTopLevelNodes will not throw any exceptions
When using self referential relationships in boolean expressions, the exists clause incorrectly uses the table names to qualify columns which will be the same for parent table and the child table. This is now fixed by generating unique aliases as we traverse down the relationships.
Better SQL generation for select queries (the query plans will be the same but much more readable). This closes some long standing issues (#6, #121, #278).
