* VariableAction stores pending connections between trees.
* Update JavaParser from 3.17.0 to 3.19.0
* Object trees in assignments and return statements are linked to the appropriate expressions.
* Return trees are linked interprocedurally.
* ReturnStmt variable actions are now all generated by VariableVisitor.
* CallNode.Return are now generated by VariableVisitor instead of the SDG after the interprocedural finders.
* Actual-in nodes are now generated based on the expressions used, and then linked to the actual-in generated by the InterproceduralUsageFinder.
* We now accept calls as scope or argument of another call.
* ClassGraph is now a singleton. ClassGraph#newInstance() generates a new one.
* ClassGraph can generate a complete ObjectTree for a given type.
* MemberNode's parent can now be any node, and can be set after creation.
* New slicing algorithm for the JSysDG.
* Added interprocedural object-flow arcs.
* Added ObjectFlow and Flow dependency arcs.
* Introduced test to guarantee that interprocedural arcs are either input xor output.
* Updated tests

* JSysPDG: inserts IO and Member nodes before generating data dependencies.
* ObjectTree is now a real tree.
* ObjectTree has string and node iterables.
* VariableAction can be cloned with #createCopy(), the graphNode is set to null.
* VariableAction.Movable can't have object tree, getter obtains inner's.

* IAF now use a map of VariableAction instead of a set of StoredAction.
* They contain a map with stored actions.
* In their state, they accumulate the tree of repeated actions.

Resolve "Flag `-o` does not work"

Closes #47

See merge request !55

Fix bad smells

Closes #53, #52, and #54

See merge request !57

Closes #53

* Closes #52
* Simplify calls and remove unnecessary searches.
* Make dotexporter functional

Closes #54

Resolve "Summary arcs must be generated between actual-in and return nodes"

Closes #51

See merge request !56

Dynamic initializerDeclaration in ConstructorDeclaration

See merge request !52

* Small regression: only the last field declared in a constructor is included. This is expected, and will be solved with the new object dependencies.
* Integrate ImplicitNode as boolean in GraphNode.
* Updated tests
* Slice now allows the insertion of implicit instructions, but does not output them when generating the AST.
* Removed list of nodes from slice, as the map contains a superset of the information of the list.

* Update tests with better slices.
* GraphNode#addActionsAfterCall uses varargs instead of a set.
* Improved handling of super() and this() calls.
* ImplicitNode is now generic
* Improved interface in JSysCFG to insert new instructions ad-hoc.
* Constructors now have an implicit "return this".
* Removed JSysCFG#getDeclarationClass, ASTUtils has a similar method.
* VariableActions can now store (but don't propagate) a tree of fields acted
  upon.
* VariableActions can now take null as variable, or any possible expression.
* Automatic generation of the actions for fields (USE(a.x) generates USE(a)).
* Conversely, fields now either traverse their scope or declare an action.
* Handling of ThisExpr.
* Better initialization naming for fields.
* Implemented default initialization of fields if none is present.
* InterproceduralActionFinders:
  * Unified the behaviour of #initialValue()
  * Improved generation of actual-in/out for fields.

Caveats:
* InterproceduralActionFinders cannot process VariableActions that don't resolve
  into a ResolvedValueDeclaration. Thus, 'this' must be declared when entering a
  method or constructor declaration.
* Removed type from IO nodes, as it required resolving expressions and was
  unnecessary for the slicer.

* VariableAction stores the real name and the variable may be null.
* VariableVisitor entrypoint must be #startVisit().

Updated variable_pattern_regex to match VariableActions regarding object fields accessed in different ways