Avoid encoding System messages

[gusty]

This is a possible micro-optimization:

By declaring the message type generic on the subject and using some ad-hoc overloading we can use direct byte array literals like:

send (writeMessage ("System"B, [userId], "Logon", pickle valueP (LString movieId))) session

additionally by making the subject generic:

send (writeMessage ("System"B, [userId], "Logon"B, pickle valueP (LString movieId))) session

alternatively instead of overloading writeMessage we can change the type of the first and third parameters, so when it's a string variable we explicitly use the pickle function as in the 4th parameter.