update cran packages
manually fix dplyr and png cran-packages
r-RcppArmadillo: update to version 0.4.300.0
cran-packages.nix: added missing sha256 fields
cran-packages.nix: drop trailing whitespace
Fix for hdevtools: update patch to build with ghc 7.8.3
Merge pull request #3610 from ts468/hdevtools

Fix for hdevtools: update patch to build with ghc 7.8.3