Feat: "Clean" install during setup.

[nynymike]

To make Jans easy to learn, we add a bunch of sample clients, scripts, and other configuration (for example a sample custom attribute). We should have a setup option for clean install, where we only install the minimal configuration to make Jans function.

[ossdhaval]

@nynymike yes, this is needed. My suggestion on implementation would be to have clean install by default, and have a switch or flag in case if dev-tooling is required. Something similar to --dev. When this switch is used during installation, it'll install sample clients, scripts etc plus it should also load test data. The ability to load test data is already available using --args="-t".