Add a script to automate demo data installation

[Raruto]

At the moment the documentation on how to create a new project is excessively verbose about it (I don't think there is even a precise section that explains how to do it). At least for the demo project, to make it easier for new developers, it would be useful to have some sort of automated system to import and create everything needed.

Related to: https://github.com/g3w-suite/g3w-client/issues/183