Identify TPA injections independently of their position

[nikohansen]

When using TPA, the tell method assumes the TPA samples in first and second position of the X and f list arguments. This somewhat defeats the purpose of the ask-and-tell interface. It seems much preferable to identify TPA samples from their collinearity with mean - meanold.

First step: a method that returns norm(x - mean) * cos(x - mean, mean - meanold) if isclose(abs(cos(x - mean, mean - meanold)), 1) and zero otherwise.