Consume output data in JSON format for better statistics

[jimbair]

In order to better provide statistics and reporting across what failures we are seeing, we need to consume rpminspect's JSON output. Failures in our log can wrap across multiple lines, making shell-style greps and cuts not ideal for reporting.

Note that rpminspect's -s VERIFY filter is not used when providing JSON, so we will need to filter out success vs failure in the payload. The exit code still works as expected.