Callback Signature classes extend Operator
Operators can be used per Variable, IO or Engine

Continue refactoring IO, ADIOS classes

Changed m_Transports from vector to map, needed by subfile manager

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

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

First working examples
To do:
Resolve conflicts
Add tests after merging with current master

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

Builds libadios2_c.a and libadios2_c.so 
Verified with and without MPI
Added nonMPI hello bp write example
Added new ADIOS2_USE_C ON/OFF cmake argument

To do:
Add C tests and cmake support for the latter

Fixed conflicts for clean compilation
Fixed clang-format
Adding free in C example

Added working example examples/hello/bpWriter/helloBPWriter.c
Changed Engine signature to resolve Write void* at runtime (required by
C bindings).

To do:
CMake infrastructure
Testing

Wrapper classes CompressBZip2 and CompressZfp implemented
Under transform/compress and adding examples and tests
Added/Modified cmake files
Makign changes to cmake from PR review

To do:
Add more tests

Bugs: 1) Missing binary mode in FilePointer fopen and FStream ofstream
transports
      2) Replacing reinterpret_cast of size_t to uint_64, not the same
on Windows 64-bit

Removed some warnings generated by Visual Studio

Added static_cast for type conversions

Refactor XML reader to restore original check on single engine
conditions and eliminate warnings. Test added.

Allow ctime and fopen "not secure" warnings: now using binary fstream as
default file IO library on Windows

Picking up config.xml from examples/heatTransfer/write/config.xml from
./build/bin/heatTransfer_write_adios2

Increased Default Maximum Memory to 200Mb
Added config.xml for the heat transfer example for memory management
(among other parameters) at runtime 

To do:
Copy config.xml to /build/bin, right now the heat transfer example won't
run in config.xml is not found

Checking std::ios_base::failure exceptions
IOChrono is off by default, each owner turns it on explicitly
Modified FileDescriptor and FilePointer destructors
Added Tests BPWriteRead for stdio and fstream
Removed IO AddTransport with vector (shoud have been there?) to enable
AddTransport in Tests