Use FindBin in generators and documentation again

[kraih]

Back in 2014 we made a change (2ccaefe), since then most of the application scripts we generate and show in the documentation contain use lib, which causes problems for our users every now and then. While we want to keep the #!perl shebang, it might be nice to switch back to something FindBin based instead of use lib. The documentation has changed a bit since then, so the commit cannot simply be reverted, some sections of the documentation also need to be updated.

[jhthorsen]

Awesome! 👍