Update on TTool icons for opening / new models and projects

src/main/java/ui/TGUIAction.java

src/main/java/ui/util/IconManager.java

src/main/resources/ui/util/Open16.gif

src/main/resources/ui/util/Open24.gif

src/main/resources/ui/util/OpenN16.gif

src/main/resources/ui/util/OpenN24.gif

src/main/resources/ui/util/OpenP16.gif

src/main/resources/ui/util/OpenP24.gif