installation: postgresql driver dependency

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
sqlalchemy: name addition for Enum types

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
ranker: fix missing column in RnkCITATIONDICT

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
sqlalchemy: postgresql types support
legacy: support for postresql engine in dbquery

* Adds dynamic loading of legacy SQL functions for different database
  engines.  (addresses #2020)