Implement verbosity option

[lionel-nj]

Is your feature request related to a problem? Please describe. It should be possible to configure the software to display logging information or not.

Describe the solution you'd like Consider adding a verbosity option with short name v and long name verbose.

[dhersz]

Quoting my reply on #1194, although I don't really know Java, I think a possible implementation of this proposal would be to wrap logging messages in a if (!quiet) { ... } block:

I was thinking, for example, that this line

https://github.com/MobilityData/gtfs-validator/blob/cec914e802571cb4ee56994dae453a7a593b091e/main/src/main/java/org/mobilitydata/gtfsvalidator/runner/ValidationRunner.java#L150

that outputs how long validation took, could be wrapped in a if (!quiet) { .... } block, thus preventing it from printed when --quiet is specified (I'm not sure how CLI args parsing works in Java, I'm just assuming the quiet param could be parsed as bool and then saved in a quiet variable).

I have no strong opinion on whether quiet or verbose should be used, but I'd like to note that the flag -v is already used as a short for --validation_report_name.