AtTimeLinks and initial commits for temporal reasoning pipeline demo

@jadeoneill, in continuation to my comment [here](https://github.com/opencog/opencog/pull/923#issuecomment-49022998), could you elaborate on how fix that error.

Additionally, I included in this pull request initial versions of files for a full-fledged temporal reasoning demo; the example was proposed by @bgoertzel. FYI, @cosmoharrigan, @keyvan-m-sadeghi.

Should not be merged. Further commits will follow.