Some work to get things compiling.
- Moved the build.rs file up one level so that it is next to Cargo.toml
- Cleaned up the cxxbridge definitions so the CXX macros could run and properly define the ffi interface
- Moved some structure definitions into the ffi module so that they could be exported by CXX into a header file. Also used a pub use ffi::{...} to make the full path not require ffi.
- Did some sample getter functions for the SMF type which was defined as an opaque rust type for CXX.