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

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

Added GetVariableBase* in IO needed by C bindings and real-time
applications, nullptr is a valid state in return.

Added c bindings test under testing/adios2/bindings/c
Updating ReadMe.md to include ADIOS2_USE_C for C bindings

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

signed char needed by int8_t in C bindings
Added tests

Added portable PathSeparator
Fixed format for bp file name

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

Makefile compiles

To do:
CMake infrastructure
Verify struct adios2_Engine  forward declaration
Add tests

Refactored IO, Variable class due to common functionality

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

Restoring std:: for cstdio functions
Removing warnings explicitly with pragmas

Removed ADIOS copy constructor explicitly, as it wasn't allowed by clang
compiler in testing/xml/TestXMLConfig.cpp

Using more portable preprocessor definitions to avoid warning on Windows
for ctime and fopen

Introduced std::throw_with_nested for bad_alloc in STLVector Capsule

Removed std:: in C function calls to avoid confusion with actual C++
only calls

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

Using language primitives in test data instead of fixed width integers.
casting size_t to unsigned long in mpidummy to remove warning on Mac

Added test for generating profiling.json
Fixed inclusion for NLohmannJson json.hpp in Test
Tested resulting profiling.json on R (jsonlite), Python (json)
and C++ (json for modern C++)

Missing file_index characteristic in BP1Writer metadata