Include a Writer capability in Behavior and rename to ZBehavior

[DamianAtWork]

We would like to support the ability to log an entry of type W as an effect within our behavior.
This would change the base effect type used by flowz to a ZBehavior.

We should then have the following:

abstract class ZBehavior[+W, -SIn, +SOut, -Msg, -R, +E, +A] { self =>
}

type Behavior[-SIn, +SOut, -Msg, -R, +E, +A] = ZBehavior[Nothing, SIn, SOut, Msg, R, E, A]

The behavior will be able to log using the following:

object ZBehavior {
   def log[S, LogEntry](logEntry:LogEntry):ZBehavior[LogEntry,S,S,Any,Any,Nothing,Unit] = ???
}

object Behavior {
   def log[S, LogEntry](logEntry:LogEntry):ZBehavior[LogEntry,S,S,Any,Any,Nothing,Unit] = ???
}