Update code generation.

Now interface permits the user to define the enclosing namespace, using
directives, using declarations, #includes.  Additionally, intermediate
variables (z's) are all allocated on the stack instead of the heap, in the hope
that the compiler can perform better optimizations of stack variables.
Add bicycle-inl.h to installed headers.
Stream print now displays steer torque.
Update generated Bicycle code.
Remove default constructor for WheelAssemblyGyrostat.