Fix Version/s: None
Ultra-faint dwarf galaxies are usually found from photometry of their bright member stars. However, these stars can be superimposed on the faint, unresolved light of the galaxy, which biases the measurement. We need to measure the PSF flux with a local background subtracted.
I originally started writing this as a background-subtracted PSF flux measurement algorithm, until I realised that simply measuring the background is all that's required (and dealing with inheritance in the measurement algorithms is annoying), and it can be subtracted from other measurements as well as the PSF flux.
Made all the requested changes and rebased against master (squashing the fixups). I'm gonna run Jenkins one last time (because I've now pulled in the SkyWcs changes) just to be sure.
BTW, the poster child of measurement plugin examples is supposed to be meas_extensions_simpleShape.
Few small clarifications on the PR, overall looks great. I'll be interested to see how it performs on faint-fuzzies. Note that you have one fixup that can be squashed.
This is really an excellent example of how to implement a measurement plugin, since it's conceptually pretty simple but gets into some gory (but important) details. A nice hack day project might be to take this and annotate what's going on block by block for the pipelines documentation, if we don't have such an example already. It would be very educational! I'll see who's interested at all-hands.