config: operate on a SourceMeasurementConfig to consolidate code

Now call:
root.calibrate.measurement.load("/path/to/meas_multifit/config/enable.py")
root.measurement.load("/path/to/meas_multifit/config/enable.py")
Merge branch 'tickets/HSC-982'
swig: prevent direct access to CModelStageResult::ellipse

SWIG wrapping this directly is a bad idea: it's a polymorphic type that
would be returned by value, but SWIG wants to do everything by pointer.
The result is confusion over lifetimes, and dangling pointers.

The element can now be accessed via CModelStageResult::getEllipse().
Merge branch 'tickets/HSC-991'
Expose method to write CModel Results as Records.

This is useful for testing purposes (e.g. Jose Garmilla's sims).
add README documenting trouble running under valgrind
Set default for includePsfBBox to False

The previous default of True caused massive slowdowns
in the CModel code when we switched to a larger PSF
kernel size, as it made us use unnecessarily large
fit regions.