OpenCV and its dependencies

depends on #1079
other configopts that were used in the old easyblock shown in #561: `-DENABLE_SSE=ON -DENABLE_SSE2=ON -DENABLE_SSE3=ON -DENABLE_SSE4_1=ON`

I'm guessing there are system-specific, but it may be useful to at least include some of those, for performance reasons?

@hajgato: thoughts?