Fix tests.
Fix the way interior nodes in solids are handled.

Add a test to ensure that this doesn't get broken in the future.
This fixes example/square_cylinder_2d.py.
Make it possible to automatically start the visualizer with the
simulation.
Create a copy of the array in LinearlyInterpolatedTimeSeries.
Call add_options for all MixIn classes.
Set default names after modify_config.
Fix description of the NTNeumann node type.