Allow turning on/off of function from file in lane

Earier we had to comment out a particular segment of code of you didn't want to
run it. Suppose you didn't want to run preprocessing then you had to comment
it out. This was a bad practice because we had to compile the code for every
such change, that made the testing slow. Ideally the code should not be changed
for usability options.

XXX: The code isn't complete. Commited so that others can see in which
directions I'm going.