add tracing of origin to output v4 config files

[baallan]

also fix minor bugs in store and time handling and formats sampler output for readability so users can tell if they got what they expected for sampler configs.

[baallan]

@nick-enoent please review the changes here and cherry pick lines that still make sense with the refactorings you may have in progress.

[tom95858]

Hi @baallan, thanks for this, can you provide more detail on what "odd things" means in this context?

[baallan]

@tom95858 'odd things' means python/c yaml parser layer behavior equivalent to:

• explicit quotes are stripped
• Nu (where N is digits and u is what looks to us like a unit string) is converted to some int according to pyyaml notions of time.
• the unit multiplier seems like it may only have 1 significant character in some cases
• where the user may normally expect implicit quoting, it does not occur in favor of time conversion.

My test case demonstrates a few of these that result in int being delivered to our cvt function.
Assuming that we will stay dependent on python builtin yaml parsing, the oddities here are sufficient that I am in favor of dropping support for time units altogether and sticking with the C-defined time parameters we have today.
I have not managed to find documented python libyaml 1.1 unit parsing rules. The time feature is apparently so disgusting in general that the yaml 1.2 specification (Which python doesn't follow) removed it.