Refactor LTM, allow selective saving

[amahabal]

Currently, when saving an LTM, the last state within current run is saved. It would be better to be able to push only the salient items and edges out instead of the whole graph.

This requires some rejiggering (mostly of LTM manager, but tweaking other LTM related classes is also a good idea)

[amahabal]

Finished the code for this. Not closing this just yet, as I should document how this works before I close this.