* 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
Fix migration logic to accommodate for non superuser permissions. Closes#567
- [x] Server
By clearing the `hdb_views` schema of existing views and functions instead of dropping and creating it again.
- [x] Bug fix (non-breaking change which fixes an issue)
### Description
Fixes#495
What component does this PR affect?
- [x] Server
### Solution and Design
Create the extension explicitly mentioning the public schema.
### Type
- [x] Bug fix (non-breaking change which fixes an issue)
