Fix duplicate slash in target paths.

There is already a slash in the path after the output directory, so the
output directory does not need a trailing one.
Fix incorrect date in filename.

args.up_to is an unparsed string, not a valid datetime.
Return table list in order usable for imports.

Fixes constraint violation when using copy_from on a dumps that include
both link_lengths and peer_count.
Fix histMax not setting peer count graph width.
Update plot defaults for current conditions.

Stock maximum peer count has increased, so peer counts can be easily
twice as high. The default probe rate is higher than it was initially,
so less of a time span is required to get enough information for a
reasonable-looking plot.
Replace iterative queries with a single one.

No need for multiple queries.