Fix github#44 (-i flag misbehaving)

Closes #44

See merge request !54

Replaced by linear lookup.

Fixes #44

Interprocedural DynamicTypeResolver

Closes #45

See merge request !53

* Closes #45
* Alters VariableAction to take Expression as argument (either NameExpr or FieldAccessExpr).
* Expands the CallGraph API
* Fixes bug where movable definitions were created incorrectly.
* Now accepting FieldAccessExpr completely.

Polymorphic call graph

See merge request !51

* Fix for SlicerTest: use StaticTypeSolver.
* CallGraph#getCallTarget is now plural.
* CallConnectors edited to iterate over targets.

Resolve "Use a specific kind of set with JavaParser nodes"

Closes #43

See merge request !50

Expected removal of repeated statements that were incorrectly included in the slice by SlicePruneVisitor without being marked as such by the algorithm.

Add DynamicTypeResolver to solve dynamic types intraprocedurally

See merge request !48

* VariableAction.Definition now includes the expression to which the variable is defined, if possible.
* Solves #44, as we require the expression in the return variable action.
* Clients have been updated to register the type solvers in the new StaticTypeSolver interface.

Create ClassGraph

See merge request !46

Resolve "Slicer.java flag -l fails"

Closes #42

See merge request !47

Small fixes for future support of nested calls

See merge request !45

* CallGraph, VariableVisitor: unify visit arguments behaviour to avoid lookup errors of calls
  by the CallGraph that were not registered by VariableVisitor.

Add CI tests on merge

See merge request !44