fixed bug in SubsetRandom function in PipelineMapping
fixed bug in SubsetRandom function in PipelineMapping

In the PipelineMapping SubsetRandom function the number of lines to extract was multiplied by 4 for fastq files but then the sets of 4 lines pasted together before counting, so 4 times too many lines were randomly sampled.
AntonioJBT/CGATPipeline_core,AntonioJBT/CGATPipeline_core,CGATOxford/CGATPipelines,CGATOxford/CGATPipelines,AntonioJBT/CGATPipeline_core,CGATOxford/CGATPipelines,AntonioJBT/CGATPipeline_core,CGATOxford/CGATPipelines,CGATOxford/CGATPipelines