Refactored step prescription to speed it up.

Should now include Context.h rather than Dispatch.h in Main.c files.

Added the EDT template GUID for each step function to the CnC context.

Use CNC_PRESCRIBE macro to prescribe steps (removed prescribeStep function).
CNC_PRESCRIBE takes the step name as an identifier rather than as a string.
The following sed command can be used to automatically fix prescriptions:

sed -i 's/prescribeStep("\([^"]*\)"/CNC_PRESCRIBE(\1/' *.c