Create a smart HDF Reader which can re-produce simulation object

[jaladh-singhal]

Currently simulation objects are usually saved to disk as hdf files. But current implementation of HDF file writer (to_hdf) don't save units and only selected properties are saved. And whenever that hdf is read, the interfaces using it have to create a separate hdf classmethod to extract information from it and then convert to quantities (to get data in same format as a simulation object gives).

It will be great if we can have a HDF Reader which handles all of this hassle, by creating a simulation object (or something very close) from the hdf file. This means we also need to enhance capabilities of current HDF writer so that the new HDF reader can get all information from HDF it wants.

This requires an in-depth analysis of how simulation object is created by a tardis run and how it is saved as hdf file, so as to convert the saved hdf file back to simulation object.