Template Stabilization

This release brings all changes from the 1.6.x-beta branch to the master branch, plus some minor fixes and refactorings.

Please note the major changes introduced in v1.6.0-beta.

Old templates will not work any longer!

You have to change your configuration!

Requires FortranCallGraph v1.4.0+ and Serialbox2 v.2.4.0+