Updated for recent eris changes; minor changes

- Optimizer overhaul (gets rid of PartyMover in favour of having parties
  register themselves as interoptimizers and handle movement themselves).
- Eris interface change, getting rid of seperate createThis, createThat
  in favour of a single create<...> method.
- Got rid of short-lived (now removed) simulation->threadModel
- Locate eris via a symlink rather than looking at ../eris
- Updated for PositionalAgent interface change (no longer accepting
  double arguments, instead requiring Position-convertible arguments
  such as initializer_list<double>s).
- Added --skip-file option to skip creating a results file