Minimum time value iteration solution of the double integrator

I've spent the last week of spare time working of a value iteration problem for the underactuated robotics subject I've been working on. In particular this has involved finding the optimal policy of how to get the undamped double integrator to the origin in minimum time (github gist of code). A MATLAB / Octave solution is available on the OCW site, so I don't feel too bad publishing this here.

This has been something a bit different for me, considering how little vectorised code I've written in the past, but has already had a big impact on some things I'm doing for a number of projects. The performance benefit is substantial, but it makes code hard to read, write, debug and test.