Resume improvements

[Beanow]

On my i5-7600K I'm getting relatively frequent crashes of the application. When using the --resume option to work around this and keep scanning, the results so far are cleared.

So my request for resume would be to:

• [ ] Preserve the number of scanned instructions
• [ ] Preserve the number of anomalies
• [ ] Continue the log in append mode (perhaps requiring/implying --sync)
• [ ] Take multi-threading with -l and -j into account

At that point, running with resume and a docker with a restart policy would perhaps be enough to run this overnight and get a more-or-less complete result to summarize.

[Beanow]

Another thing I found, using -l and -j to go multi-threaded does not resume properly as only one instruction is saved to disk.