FastVersion is a Qgis plugin for data versioning in a Postgis database
...The system uses algorithms and data structures so that information is not duplicated each time a version is created.
We recommend downloading it from the Qgis app.
Plugins->Manage and Install Plugins->Settings->Show also experimental pluginsPlugins->Manage and Install Plugins->Search FastVersion
If downloaded from sourceforge, it must be unzipped in \.qgis2\python\plugins
Mapnik is an OpenSource C++/Python toolkit for developing GIS (Geographic Information Systems) applications. At the core is a C++ shared library providing algorithms/patterns for spatial data access and visualization.