Generate schema diagram from SQL schema

Our objective is to generate the diagram from schema definition not to manually draw it.
this avoids us having to manually update the diagram each time a new field is added to a table
(which becomes tedious quickly!).

Knowing how the data is stored is also essential for developers at every every stage of development
to be sure that data is being stored in a way that makes retrieving it easy.

Starting point for research: http://stackoverflow.com/questions/3223770/tools-to-generate-database-tables-diagram-with-postgresql
Possible tool to use:
- http://schemaspy.sourceforge.net/sample/relationships.html
- http://sualeh.github.io/SchemaCrawler/diagramming.html

relates to: #3

> continue: https://sourceforge.net/projects/schemaspy/files/schemaspy/SchemaSpy%205.0.0/