Merge branch 'alessandro_branch' into 'master'

...main/java/avatartranslator/AvatarExpressionAttribute.java

src/main/java/avatartranslator/AvatarExpressionSolver.java

src/main/java/avatartranslator/AvatarSpecification.java

src/main/java/avatartranslator/AvatarStateMachine.java

...ava/avatartranslator/modelchecker/AvatarModelChecker.java

...va/avatartranslator/modelchecker/CounterexampleTrace.java

...ava/avatartranslator/modelchecker/SpecificationState.java

src/main/java/cli/Action.java

src/main/java/ui/window/JDialogAvatarModelChecker.java

.../src/test/java/avatartranslator/AvatarExpressionTest.java