Initial C bindings

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

Fixing issue #230 a bug for path in file name

Added portable PathSeparator
Fixed format for bp file name

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

Attribute template core class implementation

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

templatize PrintData() so that it can work with all types

update error message for PR #224

Fix the variable definition initialization rules and add test for Def…

fixed a size_t / uint64_t problem for macOS 10.12 and Clang 8.1.0

Set debugMode to true by default.

Implemented Transform class API, and BZip2, Zfp wrappers

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

Fix shared libs default

Fixes #210

Fixing Issue #216 Python bindings

Copy constructor was implicitly removed for ADIOSPy due to m_ADIOS.

PyBind11 needed the copy constructor.

m_ADIOS is now a shared pointer to avoid copy constructor removal

Separated MPI nonMPI test as ctest failed for MPI

Solve Issue #211 and made changes due to Windows warnings and bugs

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