change target file locations for "targets" role

[jku]

currently target files (in the targets directory) are stored like this:

file.1txt
delegated/file2.txt

Here file1.txt is in role "targets" and has targetpath "file1.txt", and file2.txt is in role "delegated" with targetpath "delegated/file2.txt". In practice filepaths and targetpaths are always "ROLENAME/FILENAME" except for toplevel targets where paths are "FILENAME".

This leads to special cases all over the code: We could move the target files in top level targets to a subdirectory as well. So original example would then be

targets/file.1txt
delegated/file2.txt

I think this is still pretty understandable?