Auto-detection of language available doesn't correctly work in CMake so
just explicitly default to OFF here and error out if set to AUTO.

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

Fixes #196

Fixes #153