Add --db-index, --db-file, --taxonomy, --db-pipe for piped db files

[yesimon]

This allows loading the database from a pipe instead of a file. This is useful in cloud platforms like AWS/GCP to load the database from an object store download and decompress on the fly, which is both faster and cheaper than storing on networked disk.

Also allows processing multiple inputs in one run. This is more important for the loading from pipe scenario because the database files are not implicitly cached in the page cache between runs.

[tomkinsc]

👍 It would be great to see this merged in.

[jenniferlu717]

I'll take a look at this ASAP (hopefully today, if not by the end of this week)

[clintval]

+1 Interested in this feature. Thanks!

[maxmaliska]

+1 also interested in this feature!

[nh13]

@DerrickWood also interest on this end.

[clintval]

@jenniferlu717 Any chance of a review or merge?

[jenniferlu717]

Apologies....we've been working on releasing Kraken 2.0 ASAP and haven't had a chance to review this. It has a number of conflicts with the current code so merging is a bit more difficult but I will try to look at it soon.....

[yesimon]

In that case perhaps it's better for me to wait until 2.0 before resolving conflicts