Merge pull request #940 from hpcugent/develop

release EasyBuild v1.13.0
add commandline override for optarch toolchain setting
added unit test.
fix unit test.
override optarch after arch check
coding by trial and error.
made unittest uglier, but works now. 100%. every time. on my machine.
fix minor remarks w.r.t. style & code organization
Merge pull request #1 from boegel/optarch_cmdline

fix minor remarks w.r.t. style & code organization
Merge pull request #949 from ebirn/optarch_cmdline

Optarch cmdline