DADA script for quality plots doesn't work with all sequence file extensions

[cjfields]

Minor error that needs to be addressed, but this line in the DadaQC.R template script doesn't work if the file extensions don't include fastq:

https://github.com/h3abionet/TADA/blob/f5e793e4af1941211315874814503f0b9f5140ac/templates/DadaQC.R#L5

This should be made more flexible, or only run one file at a time (the current version is meant to run with multiple FASTQ files if they are given, but the pipeline runs these one at a time).