Database classes based on pandas, scipy, and GAMS.
Migrated from old GAMS Python API to the new version (>42.0). Test environment currently uses GAMS 46
Added new default system_directory to gams.GamsWorkspace and gams.core.numpy.gams2numpy.Gams2Numpy instances. The default is now to look for location of GAMS installation at "/GAMS/{major gamsapi version}". With Windows as OS and gamsapi version == 46.2.0, it searches for GAMS at "C:/GAMS/46". If this does not work, then it defaults to the main GAMS installation (i.e. it uses system_directory = None in initialization).
The main effect of this is that with more than one installation of GAMS, we can set up a virtual environment with the corresponding gamsapi and the package should automatically align GAMS installation with gamsapi.