Integrate Tomcat using Spring Boot

The current deployment requires an existing installation of tomcat onto which the Geocoder can be deployed. This made sense when the tomcat java application server was shared among several other applications. However, given the current approach of a dedicated docker container with a dedicated tomcat, integrating tomcat into the geocoder provides a simpler deployment/installation process. Non-integrated deployment can still be supported as well. Spring Boot provides the ability to do this and we are already using the Spring framework, so it should be straightforward to do.