improve UX for slow-running/long-latency queries

[ctb]

e.g. sometimes gather and search take a long time, or you want to quit in the middle.

a few ideas:

• save all sourmash console output somewhere by default, flush regularly;
• and/or trap ctrl-c to do the same;
• maybe even offer resume (maybe dangerous :)
• turn on -o / --save-matches / etc. options by default, since they do little harm and consume little disk space but it is massively inconvenient when you forget to specify them!

[ctb]

related to #1350

[ctb]

it seems somewhat ironic that our solution to this simply seems to be to make everything much, much faster :)

see #1226