Allow both JSON and human-readable output at the same time

[bmah888]

From @bltierney : It'd be nice to be able to see the human-readable output of a test while it's running, but also have the JSON output saved to a file.

[wifiprintguy]

+1

[bltierney]

non trivial, but clearly useful. Anyone want to help with this?

[bmah888]

To follow-up, the three non-trivial bits are:

1. This code change would touch many places that output data.

2. In those many places are flags that essentially say "if doing JSON output, then print this, else print that", and those would need to be restructured.

3. There's only the concept of one output stream per test, where to implement this feature we would need (at least) two different output streams.