Added intel & foss toolchains

Added definitions for the intel and foss toolchains to the framework.
The idea for the `foss` toolchain is that we define it as a collection of open-source tools every 6 months. The first installment if `foss/2014b` (see https://github.com/hpcugent/easybuild-easyconfigs/issues/935).

It's possible that in the future we switch to Clang+GCC rather than just GCC for the `foss` toolchain. The name will stay in that case, and this will have to updated accordingly (which might get tricky, but we can figure something out).

Existing toolchains will still be supported, so `cgoolf` is here to stay.

The main idea is to use `foss` and `intel` as common toolchains, and figure out how they should be composed every half a year.

Of course, nobody is obliged to join in on this. It's something we will standardise across VSC sites, and others are welcome to join us. Pull requests for other easyconfigs are still very much welcome (and we will definitely keep experimenting with others too, e.g. to figure out what `foss/2015a` and `intel/2015a` should look like, etc.).