Create LSSTsim processing example for SW User Guide

Create a worked example in the Software User Guide of processing raw data with obs_lsstSim. The example should include:

• Pointers to documents for creating multi-band, raw datasets with PhoSim
• Creating a data repository for the data
• Creating an astrometry_net_data repository
• Processing raw files through processCdc (including ISR, measurement, etc.)
• Creating a catalog of measurements
• Visualizing the output using existing tools

It is possible to work initially with a limited set of data (a raft, or CCD), and to start with eImages rather than raw; the example can be elaborated in due course.