"Add Spring Boot starter" as a maven pom.xml code generator

[AlexFalappa]

It would be useful to get assistance in adding Spring Boot managed dependencies in pom.xmls of existing projects.

The starter's maven coordinates and other metadata (BOMs and extra repositories) are exposed by the Spring Initializr web service in a currently undocumented endpoint: https://start.spring.io/dependencies{?bootVersion}

[snicoll]

See spring-io/initializr#371