* Enables output of Linux OS packages for CentOS 7
* Changed vendor to RStudio
* Added post install script to swap in openBLAS shared library
* tidied up some dependencies
* Added a post remove step to cleanup install dir
As we swap in the openBlas shared object file during installation
the RPM database knows that the RPM installation has been "interefered"
with. Because of this `yum remove` does not clean out the full directory
tree. This update therefore prunes the directory tree at
/opt/R/R_VERSION
