Nth PR on develop branch for easybuild-docs, for N=5

still bits and pieces to improve, but ok to receive the first round of feedback
EasyBuild provides a significant amount of easyconfig parameters (<refer to easyconfigs definition in concepts page>). An overview of all available easyconfig parameters can be obtained via ...

don't use "configuration options" here, be consistent (configuration options are the options listed in `eb --help`, these are easyconfig parameters)