Updates to linkedlist

Changes made during PR to quiver-dart
Added generators to dart
Removed generator from spatially.base

After a chat with lasse on dartmiscc, decided it wasn't a good idea for spatially
New implementation of graph.

More rigid seperation between labels and edges enforced
Deprecated Array.

There's no reason to have an explicitly non-growable list type, so
deprecating array is the best option
Removed Array and CoordinateSequence classes

After a bit more experience, List should be capable of handling whatever
spatially throws at it