Missing cmake FCInterface macro FC_GLOBAL for non-MPI function

Reorganized bindings components to map ADIOS2 core classes
Using cmake FortranCInterface to automatically resolve name mangling

InquireVariable/Attribute working for valid name, but returning invalid
type

ADIOS constructor now has host language so bindings can change define
this at the constructor level

Separated C bindings from C glue (added) for languages using C-API (e.g.
Fortran)

BPWrite_c -> ctypes
XMLConfigTest.TwoIOs -> Test BP Writer 1

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

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

Testing and Examples issues after merging with master for conflicts
Fixing non-MPI issue
C enums and Fortran parameters now compatible

Subroutine based, calls the C bindings using opaque pointers
Working helloBPWriter_f in MPI and nonMPI examples
Separated MPI and nonMPI interfaces in Fortran and C
Passing character array by trimming and adding char(0) null terminated

To do:
Add testing