replace default json serializer to improve readability

[maloel]

The default JSON serializer is done not in a very customizable fashion.
The default output is very naive and verbose, putting every single value on its own line, causing JSON dumps to take many many lines that make it hard to read.

E.g.:

    "principal-point": [
        317.4702453613281,
        237.2671356201172
    ]

Will now be:

    "principal-point": [317.4702453613281,237.2671356201172]

To do this, we have to override the default operator<< that json uses. This collides with the default implementation, so we disable json's default I/O, but this has other impacts.

Still, everything seems to work, but it adds many lines of code most of which are simply copies of the original.

Note we cannot override json::dump().