Support for UMIs

[holtgrewe]

UMIs should be configured by the Demux Web user and setting demux_reads.

For starters, we will only support this on a per-flow cell setting based on demux_reads.

<num>M will be used for molecular barcoding. In the case that the sequence is ligated to the template, bcl2fastq2 should be able to handle this. If the UMI is an index read, we will have to fall back to Picard.

[messersc]

As discussed, this issue is more about user-configurable bases masks (demux_reads) than the use case with UMIs going to a separate fastq, as this was possible before with picard if set up correctly.

#7 adds the capability to parse demux_reads and match it with planned_reads, check it for consistency and return a bases mask for bcl2fastq2 (e.g. y100,I8) or picard (100T8B).