The PPDG makes some transitive CDs direct, in order to
remove some of them. The ES-SDG then stops some of these,
which had the consequence of not reaching `Enter` in some
cases.

* Removed null pointer when type is not specified
* Improved usage message
* Clarified error messages

# Conflicts:
#	sdg-core/src/main/java/tfm/graphs/CallGraph.java
#	sdg-core/src/main/java/tfm/graphs/cfg/CFGBuilder.java
#	sdg-core/src/main/java/tfm/graphs/sdg/MethodCallReplacerVisitor.java
#	sdg-core/src/main/java/tfm/graphs/sdg/SDG.java
#	sdg-core/src/main/java/tfm/graphs/sdg/sumarcs/NaiveSummaryArcsBuilder.java
#	sdg-core/src/main/java/tfm/nodes/type/NodeType.java

Removed WIP and development guidelines.

* Migrated `NodeType`s to specific `GraphNode` child classes.
* Revamped creation of SDG
* Added ASDG and PSDG, based on the APDG and PPDG.
* Improved handling of variable usages, definitions and declarations.
* Added movable variable actions, that can be placed in a CFG node and
  then relocated to their own PDG node.
* Added fix-point and specific slicing algorithm to summary arc
  generation.
* Documentation of most methods (public and private).
* Removed unused elements.
* Fix possible errors by migrating all maps whose key is an AST node
  to IdentityHashMap.

Es sdg

Create a user-facing interface CLI

Previously, those that did not perfectly match were discarded and left unconnected.

* DataDependencyArc: change style
* Exit/ReturnNode: removed variable extraction
* ESCFG: removed the method call as an exception source.

Other changes: corrections, improvements and API simplification