Add a log when the publiccode.yml is 100% correct

[tomootes]

Currently there is no output when there are no errors. I would like to see something like logline saying: "This publiccode.yml doesnt contain any errors."

[bfabio]

Good point! The fix belongs in the CLI (publiccode-parser/publiccode_parser.go). A PR is welcome!

[tomootes]

@bfabio i'll try to make some time. Shouldn't be too hard this one.