[config.opts] use gcc-release from configs
[external-libraries] update virtualenv
[external-libraries] add builddir to python path
[external-libraries] update virtualenv
[external-libraries] do not add builddir to pathon path

This lead to problems with more than one build of the same shared object
(not clear which one was found), use ipython instead (which always takes
the local one).
[dune-fem] update
[dune-pdelab] update
[dune-stuff] update
[local.bin] update
[dune-grid-multiscale] update
[configs] update
[dune-pymor] update
[dune-gdt] update
[dune-hdd] update
[pymor] update
[README] update