core: experimental introduction of adapters
labs/pwm: fixed incorrect use of quantile
jaspar: added access to another sub-collection
various stuff jaspar, core and ucsc

- jaspar: added CNE collection
- core: let exceptions go so that they are printed
- Ucsc.string_of_genome exposed
core: fixed several bugs in evaluating a pipeline

- fold function was wrong for merge case
- added a fold_deps
- still nothing to prevent that a node is visited twice during the fold (would be easy though, using hashes)
Introduction of map pipelines