Separate seconds_interval arguments for messages and files

[wlandau]

Following up on #1055: console messages and metadata files are very different in terms of performance, We want to print console messages reasonably often (every 0.5s) but maybe only write to metadata every 15s or so. It doesn't seem like a batched append operation every 15s would be much of a strain on a shared file system (@rpodcast, we can check tomorrow).

[wlandau]

As part of this issue, I will consider printing console messages when metadata files are written, at least for the verbose and verbose_timestamp reporters.

[wlandau]

Fixed.