The parsing routine should be able to be used for GSM 04.08,
08.08, ISUP and other parts. It should allow to have variable
sized length and tag fields etc. Right now it is not yet doing
all of what it should do.
E.g. the order of optional entries can be different, the code
assume an order right now.
* Use parameterName instead of name to avoid funny effects.
* Handle tag only classes as fixed field with a zero lengthLength
* Make the structure classes return an instance of itself. This
is a bit weird and will need more thinking.
Remove the need to create an instance of this class. So we either
need to make this totally instance based and hold the dictionary
in the ISUPMessage or we can keep it class based. I am not sure what
is best right now.