Slicing criterion can include a variable. Multiple criteria can be included for a single file.

Add polymorphic calls

See merge request !61

* Call targets are computed based on static types (same as variable action's dynamic types).
* Usage and definition finders now deal with accumulating information in the same variable action ('-arg-in-' or '-scope-in-'). That variable action is created in the VariableVisitor, and the transference is prepared at the end of the finder, instead of with each handleActualAction.
* ObjectTree: pattern now accepts any variable, including fake patterns like ('-root-' or '-arg-in-')
* Tests updated

# Conflicts:
#	sdg-core/src/main/java/es/upv/mist/slicing/nodes/VariableAction.java

* Some searches in object trees may return multiple nodes (e.g. "var.A.x" and "var.B.x" for "var.x")
* Only leaves in object trees can be the target of summary arcs.
* Polymorphic nodes aren't interconnected with data dependencies.
* ClassGraph's map now split into kinds of vertex.
* ClassGraph's vertex now generic.
* Polymorphic member nodes cannot be leaves in object trees.

Dynamic types are computed from the descendants of the static type, without further analysis.

Update JavaParser and remove bug workaround.

Closes #60

See merge request !59

Object flow and trees

See merge request !58

* Some assertions changed to Illegal{State,Argument}Exception.

* Unified both summary arc analyzers
* Deleted unused code.
* Converted checks into assertions
* Removed some bad patterns, including a possible bug in BinaryExpr handling.

If a variable is provided, only nodes that represent that variable (or its MemberNode, if object) will be selected.

Related tests updated.

this test requires improved variable targeting

When searching for interprocedural actions, don't generate trees for variables that don't have them.

Redesigned JSysCallConnector, to rely more on CallConnector.