Summary

This is a major production release with a variety of new features and bug fixes in the areas of staging, HDF5 compatibility, and writer aggregation.

Features

Hierarchical traversing for reading ADIOS files using the new Group object
- This is an optional, alternative way to go over the variables and attributes in a file/stream in a similar fashion as one traverses HDF5 files.
Default aggregation mode has changed to 1 sub-file per compute node (from one sub-file per process)
DataMan engine supports compression (used for wide-area-network data transfers)
SSC engine supports flexible I/O pattern
Step selection for reading
Simplified wrapper bp2h5 for the adios2_reorganize utility for converting ADIOS BP files to HDF5 files.

Added a VOL plugin to enable ADIOS I/O through the HDF5 API. Basic functionalities are covered.
Enables existing HDF5 clients to create and access ADIOS files with minimal effort.

Double pointer Get API for the Inline engine
AggregatorRatio option to set number of sub-files as a ratio of number of processes. NumAggregators option is used to set a fixed number of sub-files. See options for https://adios2.readthedocs.io/en/latest/engines/engines.html#bp4