Provide for separate Context types for named statemaps.

[corneil]

The push operations will provide for a Lamba to obtain the relevant context.

An example is the Packet Reader the collects a byte array for the data and the checksum. These to can be a single named state map with a push into the machine. The context will be with reference to a mutable byte array in the parent and the termination character(s). When reaching a termination character a pop will send back to the previous state in the parent.