Improve the safety and uniformity of the HDF5 importers

HDF5MetaDataReader, HDF5DataReader and ExperimentImporter shared almost the same structure and contents (only the HDF5-Group keys were different). Therefore, templates HDF5MetaDataReader and HDF5DataReader is made to unify them, and remove code duplication. Currently, the templates distinguish between a LegacyReader and a ExperimentReader; the LegacyReader may be deprecated later to increase uniformity.

Redundant module ExperimentMetaReader and ExperimentDataReader are removed.

Previously, Blosc-filter resources were not released after initialization; hence, HDF5BloscFilter module is added to use Blosc filter in a safe and uniform manner.

Resolves issues #275 (closed), #277 (closed)