Add swagger-generator module to Dockerfile

This is needed because docker build will otherwise fail due to maven
complaining about missing modules

Author: Blackclaws

Dockerfile

@@ -18,6 +18,7 @@ COPY ./google_checkstyle.xml ${GEN_DIR}
 COPY ./modules/swagger-codegen-maven-plugin ${GEN_DIR}/modules/swagger-codegen-maven-plugin
 COPY ./modules/swagger-codegen-cli ${GEN_DIR}/modules/swagger-codegen-cli
 COPY ./modules/swagger-codegen ${GEN_DIR}/modules/swagger-codegen
+COPY ./modules/swagger-generator ${GEN_DIR}/modules/swagger-generator
 COPY ./pom.xml ${GEN_DIR}
 
 # Pre-compile swagger-codegen-cli