Add basecalling support

[hoelzer]

If a folder with FAST5 files is provided perform basecalling with guppy and then start the assembly pipleine.

see
https://github.com/replikation/docker_pipelines/blob/master/modules/basecalling.nf

[hoelzer]

Actually this would be a really good feature because the pipeline has then full control over the model used for basecalling that can then be subsequently used for polishing in medaka