Initialises the aspects and the aspect value labellers
in the aspect model. This should be called after the constructor
has been run.
Implementations of this class should always start by calling
the initialise method of their super-class, if such a method exists.
This use of initialise enables us to separate the resource intensive
initialisation process from the constructor process. This can be useful
if there are ways to avoid the initialisation process because of information
that is already available, eg in another aspect model. In particular,
this is useful for aspect model duplication.