simultaneous fitting across multiple images

[PaulHancock]

Desired feature: For Aegean to be able to fit across multiple images at the same time. Examples:

• given a set of I, Q, U, V images, fit a single location/shape but 4 flux values
• given an image I and a variance image S use the combined SNR to detect sources
• given a cube of images, fit a single position, multiple fluxes (ie make an SED)