Include run information in the vlsv files

[ykempf]

Things we notice in practice get lost or hard to retrieve and match with bulk files, and which would be useful and inexpensive to include directly in Vlasiator VLSV files:

• copy of the cfg file;
• copy of the version string;
• run ID;
• some run information (path, run name if not visible in path, copy of job script)?

[sandroos]

You can add these to the xml tags, they shouldn't mess up anything as vlsv will skip all tags in footer it doesn't recognize.