Grading mode sounds a bit more specific now
Various Picobot test improvements

The maximum step limit for simulated Picobot programs has been
put into use. Errors show up with more detail in the grade file,
and the grader sees the number of steps taken to simulate the
Picobot program on the command line.
Picobot now ignores program lines not starting with a number

Students may decide to put their names or contact information in
the Picobot program file. If these lines do not start with a state
number, they are treated as comments.
Added error for empty Picobot program