Add time series charts for a point and kernel

[drew-bower]

Given a point or a point and a radius distance, and a ordered series of rasters, compute a time series graph.

Optionally it would also be useful to provide input for multiple rasters, then superimpose all lines on the same graph.

For the kernel operation it would be useful to have options for unweighted focal mean

[drew-bower]

As well as distance decay focal a mean.