Replace configuration file with wizard-like interface

[esyriani]

The configuration of a project relies on a web-based Xtext editor and Xtend code generator. Although it is a useful editor, the user needs to know the syntax and the possible variants. Also, the text file is written in a programming-style fashion. We want to replace this module with a more user-friendly editor of configurations. The new editor will be generated by Gentleman to support a projectional editor for defining configurations. Then we need to develop a code generator that produces the php file as it currently is the case.