Combined old subprocess plotting stuff into one new py3 script always producing one stack plot. Use -h for help

Switch back to differenty named methods for now to return uncertainty vectors to Python numpy arrays

Fix missing LDFLAGS for HOPPET; fix warnings for unused variables in conditional compiling; update CL, NEWS

Remove requirement of recent env executable to ensure C++/Python unbuffered output; add env. var. to environment instead

Better printout

See merge request qcd-public/fastNLO!3

Patch new nnlojet-combine to use APPLfast naming for weights as in previous versions to avoid issues with current LAW workflow