* Modification to R environment
This PR modifies how the R environmnet is presented, and fixes
installing the standalone Rmath library.
- The Rmath build and install methods are combined into one
- Set parallel=False when installing Rmath
- remove the run environment that set up variables for libraries and
headers that are not really needed, and pollute the environment.
* Add setup_run_environment back
- Add back the setup_run_environment with LD_LIBRARY_PATH and
PKG_CONFIG_PATH.
- Adjust documentation to reflect the current code.
71b9e67b3c