Additional new line needed in `dada()` verbose output

[mikemc]

The dada() verbose output typically ends with something like

   selfConsist step 2>

where the ">" is the prompt. It seems to be happening because the last printed line comes from the cat() call at https://github.com/benjjneb/dada2/blob/7475928d4691507772ce79ed92c99f438dea7af4/R/dada.R#L331 which lacks a final newline character. I've been putting off making a pull request myself because I'm not 100% on where to put the new cat("\n") so that it will be correctly called/not called in all cases.