Add other interpolation methods to the area between curves method

[cjekel]

Right now the area between curves method uses bisection of largest gap to add artificial data points. This method was used to minimize the number of artificial quads/points. However, this can have some negative effects in some cases, specifically when the sampling rate is artificial and does not match (e.g. one curve is just a straight line with few points).

A potential alternative it to use the arc length projection of one curve's points onto the other. This would preserve the sampling rate, and may make for more uniform quads. This is similar to what's done in PCM method.

When another interpolation method is added, give users the choice of which interpolation method to use. Changing the interpolation method is anticipated to change the results.