Create a compare ORT command

[sschuberth]

In several scenarios, one may be interested in whether two ORT (pipeline) runs yield the "same" result (modulo some varying fields like timestamps etc.). Use cases include:

1. Verify that a new ORT version does not unexpectedly generate different results when scanning a "gold standard" project in a fixed revision (and with a fixed configuration) again; i.e. use it as a check in end-to-end / integration testing before taking a new ORT version into use.
2. Verify that a configuration change for a fixed ORT version does not cause any difference in (unexpected areas of) the result.
3. For a fixed ORT version and configuration, see the difference in results between two different revisions of the same project.

The idea is to start with a trivial implementation for use-case 1. that just tells whether two ORT results are the same or not, without actually "interpreting" any differences on a semantic level that pays attention to the structure of the data model.