- $version does not exit anymore in css-variables.css. now its value is computed during setup and equals setup timestamp instead.
- use precompiled files (declared in datamodels XML files) to check if theme compilation is required or not.
- referenced images in scss files are included in precompiled file signatures just like scss files md5sum.
- images declared in scss files with v=$version are reloaded automatically on browser side after each theme compilation (see xxx.png?v=timestamp)
- precompiled files are replaced if theme compilation occurred. this will avoid same time consuming operation at next setup.
- code cleanup: arrays / variables renamed
