Streamline the result object

Our largest source of bugs right now are caused by deepdish handling of h5 files. I don't think there is any need to move away from deepdish (which was initially chosen just because it had an easy-to-use interface), but if we do the following, things will be much easier

• Make all arrays in the deepdish file named numpy arrays rather than pandas data frames
• Ensure that everything else in the deepdish result file is either a string, float, list or dictionary of these things.

During this process we should check that the results files are not dependent on bilby (@charlie.hoy reports this is not the case at the moment).