beesh: remove unused and deprecated variables R and W

use BEEWORKDIR instead of W
and BEEPKGROOT instead of R
buildtypes: Add support for R packages

use BEE_BUILDTYPE=r-package to build r packages.

r packages are currently not detected automatically
bee-init: Add support for cran repository in url rewriting
Merge branch 'cran'

* cran:
  bee-init: Add support for cran repository in url rewriting
  buildtypes: Add support for R packages
  beesh: remove unused and deprecated variables R and W