[IMP-dev] GPU cuda autocompilation in IMP

I added an apparently operational cuda auto-build (any .cu file placed in src or src/internal should work). It seems to work fine but let me know if it causes havoc.

Important note - the cuda build system hates the IMP namespace, specifically. Perhaps its some internal cuda macro. It means we cannot include <modulename>_config.h in any cuda files, for now, and need to add a bypass if we need to access an IMP method or object from cuda code.

Barak