Add option to write extended truth information.

[cwwalter]

Currently, we write the centroid files, but having the option to also write extended truth information at the pixel level would be quite useful for many simulation based studies, analyses, and visualization including de-blending and complex reweighing and emulation work.

As a first step, storing the postage stamps and location for each galaxy along with a separate plane for the sky background would be a good start. There are likely smarter and more compact ways of storing the information.

[cwwalter]

In the new architecture, this feature will be tied to the collected photon lists described in #244.