qcfasta error message

[Alejandra Cervera]

if readkey and matekey are not defined correctly errors occur in linking the images folder from fastqc to the right places. This seems to be difficult to debug and it is a common mistake to not set them up properly. I think the function should check that the image folder with the readkey exists before attempting to make the link and report the problem clearly so the user can fix it without having to look at the functions code. So checking mechanism should be added prior to linking stuff in readsFolder instances.