WIP Galaxy tool to relabel samples in a "list-of-pairs" dataset collection

[pjbriggs]

PR that attempts to address issue #18. The relabel_samples tool takes a dataset collection (a list of paired FASTQs ) as input along with a list of sample names, and creates a new collection with the same pairs but relabelled using the names from the list.

There are some issues with the initial version:

• Duplicates the datasets from the input collection unnecessarily (and also eats up disk space/user quota)
• No sanity checking that number of pairs matches the number of supplied names
• No way to specify the original name to be relabelled

[pjbriggs]

See a vastly better implementation of a relabeling tool by @jmchilton via galaxyproject/galaxy#3603

This implements the operation within the Galaxy core and doesn't duplicate the dataset elements from within the source collection when creating the new version.

[pjbriggs]

Closed, we will use the relabeling tool from the core Galaxy instead.