Experiment.py: update mklink to be able to construct relative links (uses new function commonprefix), and use this option in ExperimentList.__linkToFile() to make relative links to primary data files.
Experiment.py: update mklink to be able to construct relative links (uses new function commonprefix), and use this option in ExperimentList.__linkToFile() to make relative links to primary data files.

fw1121/genomics,fw1121/genomics,fw1121/genomics,fw1121/genomics,fw1121/genomics