Implement multiframe capture; closes #46

[philipbelesky]

Implementation as discussed/described in #46. It seems pretty robust, however a high number of keepFrames is not particularly performant, I assume just due to Rhino displaying so many meshes at once.

The implementation doesn't handle spacing at all, so generally users will want to use a series to space out the objects. This also only makes sense with a manual, or very high tick rate, and with frame averaging set to a low number. When used this way it is an easy way to take a series of 'snapshots' of the models and (if you setup the timing well or use data dams) to capture dynamic behavior such as the effect of water/wind used for analogue simulation.

[mariuszhermansdorfer]

Looking good. Let's merge this.