Add constraint removal capabilities to FullSTN.

It is also integrated in all unit tests for STN.
Introduce an immutable list usable from java.

This is basically a wrapper around scala's immutable list.
It is used in FullSTN to record all added edges without impacting to much
the memory footprint (most part of the list is shared between multiple
instances thanks to its immutable structure).
[0.4.5] Import refactoring that makes most STN operations defined in final classes.

Hence implementing classes have just a few methods to implement (those are u
used for all other operations). This make implentation classes much more
compact and avoid code duplication and dumb mistakes.

An STNU manager is now implemented that maintains a full STN (with
floyd-warshall) and checks if contingent edges are tightened.

Refactoring of most unit test as well. They now apply on all subclasses of:
 - ISTN
 - ISTNU
 - STNManager
 - STNUManager
Add a method in EDG to compute all-pairs shortest paths.

Make sure rule are applied on triangles (in some corner cases, there could
been the same node twice).
Added an initial implementation of MMV.

It is valid as an STN but there is still some bugs on Dynamic controllability
checking (see units tests for that).
WOrk on constraint and variable removal in FastIDC.
Also proposes a basic dispatcher
Implemented variable removal in FullSTN.

latest/earliest start is left unimplemented in FastIDC (throws unimplemented
exception) since it is not sound.
It is implemented in dispatcher at the cost of running apsp after a
propagation.
Integration of previous change in GenSTNUManager and GenSTNManager.

Those two abstract class provide all operations on STN/STNU that are usable from an external component. Those provide ways to extract both timepoints and
constraints with the appropriate flags (contringent, controllable, dispatchable).
[O.5.0] Implement missing functionality for usage in FAPE

Added a way to unify, temporal references with start/end of the STN.
Bellman ford is now used to provide earliest/latest start in FastIDC.
Important performance improvement in the computation of the APSP graph
in the STNUDispatcher.