Topological order

The idea is to sort addins in a topological order. Each addin can define one of five things for _order_:
* `>X` - I must be immediately after the addin with id X

* `>>X` - I must be somewhere after the addin with id X (but not necessarily immediately) 

* `<X`- I must be immediately before the addin with id X

* `<<X` - I must be somewhere before the addin with id X (but not necessarily immediately) 

* `Number` - A numerical order which is used if none of the above is applicable


This is again a styling issue and not related to saving 'else' or anything like that. The story tells you that you need to find a cluster by addin id and if you fail then stop right there, no need to continue doing anything because this is a critical error.