Externalize config

[danlangford]

to address #2 this updates the codebase to a more current version of Spring Boot. i also added some best practices to the pom file and spring project configuration. most importantly i migrated from Test.properties to application.properties in an attempt to quickly take advantage of Springs built in support for externalized configuration. all you have to do is create your own application.properties in the same directory as the jar and Spring will consider it when looking up properties, and consider it in a high priority than the files in the jar. https://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-external-config.html. Also another major change was the use of Spring @ConfigurationProperties to quickly map all the properties to a type strict POJO for easy access.