DM-1015 Simplifies GaussianFlux algorithm by using slots to calculate centroid and shape.

Remove the config options fixed, centroid, shape, and shapeFlag
Remove code from GaussianFlux.cc which is required to support the non-fixed option
Code is now equivalent to the previous setting fixed=True, centroid=current centroid slot
shape=current shape slot, shapeFlag=flag of current shape slot.

Now that the shapeFlag can cause GaussianFlux to fail, modify unit tests accordingly
Merge branch 'master' into u/pgee/DM-1015

Conflicts:
	src/GaussianFlux.cc
Fix to DM-1015 to ensure that the result is created prior to failure
Merge branch 'u/pgee/DM-1015'
Fix xy0 bug in SdssShape centroid

Legacy core of SdssShape works in LOCAL coordinates, but we need to output
in PARENT to be consistent with all other measurement algorihtms.
Merge branch 'u/jbosch/DM-641'
Fix too-long lines in Swig interface file.
Fill and attach metadata in algorithm test utility code
Move low-level Sinc photometry code to a new file

This undoes some of Perry's work on DM-1067, but it's overall
a bigger cleanup and it allows us to start moving the aperture
flux implementations to a new algorithm class.
Add ApertureFluxAlgorithm base class for multiple-aperture fluxes
Add concrete algorithm class for circular apertures