4.2

- background GRU tasks
- asset generation
- preforking and DBus IPC
- ISO download on job schedule (via GRU task)
- tidyfied code
- many bugfixes, many new bugs

Revert "ignore stale qemu.pid files" and give isotovideo more time

to kill qemu - we'll see

remove the paragraph about OPENQA_HOSTNAME completely and fix asciidoc