Toolkit2: Should have --pretend and --clean option

Every invocation of the toolkit currently overwrites certain files. However, as a user, I miss two options:

• Clean the generated files, especially the glue files. For a novice user, it is not obvious what to clean when wanting certain files to be regenerated. A --clean file should exeute rm Abstract* KernelCalls*

• Explain what the toolkit would do. Some tools such as rename(1) or rsync(1) have an option called --pretend, --dry-run or --no-act which explain what the tool would do. We should offer such an option to make it more transparent what especially a second run of the toolkit does.