Filter out hidden files for analysis results endpoint

[atruskie]

e.g. for staging.ecosounds.org/analysis_jobs/system/audio_recordings/188257

It currently returns:

...
{
"path": ".dates.txt",
"name": ".dates.txt",
"type": "file",
"size": 87,
"mime": "text/plain"
}
...

Follow a more unix-y convention of not showing hidden files.

The idea here is that our system level files (e.g. logs, system configuration, and other non-user stuff) can be stored inline with results and not exposed to users... without the need to resort special case filtering for special directories / files not meant to be seen.

[atruskie]

👍