Improve coverage of analysis.py

[sgherbst]

Some of the key areas with low coverage are:

• Exercising the command-line mode (have to figure out a good way to do this while gathering coverage information)
• add_sources function
• set_generator_option function
• view function (this one is tricky because it involves launching a GUI -- the most we could do is check that it doesn't crash)
• pack_results / unpack_results