Use named constants for RHost filename and relative R binary path.
Use named constants for RHost filename and relative R binary path.

AlexanderSher/RTVS,MikhailArkhipov/RTVS,karthiknadig/RTVS,AlexanderSher/RTVS,MikhailArkhipov/RTVS,AlexanderSher/RTVS,karthiknadig/RTVS,karthiknadig/RTVS,MikhailArkhipov/RTVS,AlexanderSher/RTVS,karthiknadig/RTVS,MikhailArkhipov/RTVS,karthiknadig/RTVS,MikhailArkhipov/RTVS,AlexanderSher/RTVS,AlexanderSher/RTVS,karthiknadig/RTVS,MikhailArkhipov/RTVS,MikhailArkhipov/RTVS,AlexanderSher/RTVS,karthiknadig/RTVS