bump version to v3.1.1 + add a couple more extensions to sync with R v3.1.0 easyconfig

@hajgato: syncing up both PRs proved to be very painful because you've reordered the extensions, and also because of dependency updates (libpng, which includes a zlib update, causing conflicts with other stuff in flight on my end)

But, there's another option: just bumping the R version to v3.1.1! :)

I also added the missing extensions I have in https://github.com/hpcugent/easybuild-easyconfigs/pull/908.