Included some error messages.

src/main/jastadd/Analysis.jrag

src/main/jastadd/Errors.jrag

src/main/jastadd/Navigation.jrag

src/main/jastadd/Ros2Rag.relast

src/main/jastadd/backend/Generation.jadd

src/main/jastadd/backend/Mappings.jrag

src/main/java/org/jastadd/ros2rag/compiler/Compiler.java