BP3 Deserialization:
Getting subfile seeks and intersection info
Set host language in bindings for row-major and zero-index info

Passed ctest (MPI and nonMPI) excluding ADIOS1 engine, and Python bindings
HDF5, C bindings and C++ tests working
Introduced BeginStep EndStep functions
Renamed IO GetVariable/Attribute to InquireVariable/Attribute

Getting and defining available Variables at Open
Storing Variable position in Metadata, added to VariableBase
mpidummy: Added support for MPI_Reduce, MPI_Gatherv
Added utils and BPLS

Implemented basic buffer reading functionality
Added threading for bp serialization/deserialization
Refactored MPI functionality
Engine is now a reference
Initial Read API