Various Jenkins-related tweaks.

-) created a .profile at the root of the docker image - seems the new nvm script requires that.
-) installing simplejson and mako python packages, for the sanity check.
-) calling prepare_travis.sh in order to try and download precompiled packages for openssl and protobuf.
-) using the new "config" axis.
-) improved the output of prepare_travis.sh.