Allow reusing lookup tables

[larshei]

One of the strenghts of this state machine is, in theory, that you could

• define one set of states/transitions tables
• create mutliple instances based on the same tables
• that way, you can easily create systems that use the same function multiple times, e.g. handling multiple incoming connections or multiple interfaces of the same type.

On creating a second instance, a user may pass the same transition and function table as previously passed to the first instance.
However, for the second instance the lookup tables will be newly created. Therefore a second lookup table set will be generated that should be identical to the already existing lookup tables from the first instance.

Add an init function that inherits most of the data from an already existing state machine instance.
(basically everything but the user data?)
Make sure to count how many contexts a table is currently being used in.
Free lookup tables once not needed anymore.