Investigate switching from HAL Browser to HAL Explorer

The HAL Browser which is included in Spring Data REST by default is seemingly unmaintained (and has at least one known security issue):
https://github.com/mikekelly/hal-browser

Known security issue: https://github.com/mikekelly/hal-browser/issues/99

Spring Data REST developers have begun to move away from the HAL Browser in favor of the HAL Explorer as noted in this comment from a Spring Data Rest developer and as evidenced by this ticket: https://jira.spring.io/browse/DATAREST-1386

Additionally, Spring Boot is looking at moving to the new HAL Explorer module by default: https://github.com/spring-io/start.spring.io/issues/184

We should investigate switching to "spring-data-rest-hal-explorer" module based on https://github.com/toedter/hal-explorer (which is an Angular based HAL browser)

However, we would need to port any custom code (including our custom Shibboleth login code) from the HAL Browser over to the HAL Explorer.