Guidance: Implement capability to have multiple configuration

[GFlisch]

A Group can contain multiple companies having different configurations: for database servers or authorities. Implement a multi-configurations capability and let the user decide, via a dialog, which configuration is appropriate when he/she is starting a new project. If only one configuration exists, no dialog is displayed.

The Guidance.json file will remember the choice done.

When the application is started, if the Guidance.json doesn't contains (current implementation) the company (key used to identify the configuration) the dialog will appear (if there are more than one configuration) to let the user select the configuration to use.

[GFlisch]

Implemented. Will be part of the next version of the Guidance. 2021.2.12