svd_utils and Cluster both use this function now

resume partial computations, interrupt computations, timing, writing at
regular intervals, better print statements to guide users, timing, etc.

check_for_matching_attrs now checks an h5 object against a dictionary
buildReducedSpec now returns a list with empty strings for single steps
get_formatted_labels now throws exceptions instead of warnings and
returning None

Printing reminder and instructions on aborting and resuming compute()

* Checking for partial results
* Resuming from partial results
* Automatically resuming / returning completed duplicates
* use_partial_computation will automatically take the last partial grp