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 looks like you want a Set api and are implementing it with a map, which is ok but clutters your code.
i would search for a simple set implementation.
then you'd have 
currentCluster.dependsOnClusters.add(cluster.id)
and later
currentCluster.dependsOnClusters.contains(someId)
which is more abstract