Added code to opDispatch to make a full example that can be copy, pas…

[MikeShah]

Added code to opDispatch to make a full example that can be copy, pasted and run. I believe this will more clearly help users understand opDispatch. For clarity, I changed the incoming type to spell out 'Type'

[ntrel]

BTW There are other examples such as here that don't declare main.

[MikeShah]

BTW There are other examples such as here that don't declare main.

My thoughts are for the call logger example it is something new enough enough that a beginner might want to copy & paste. :)