[Sprint: 39] [master+backport] XD-2377 Update "About" section in UI with relevant release links

* Provide XD version info via `/management/info`
* Add AngularJS service to retrieve version info
* Add version info to About page

Jira: https://jira.spring.io/browse/XD-2377


Accessing the hardcoded management context path `/management` to get the build information will not work if XD is configured to use custom management context path `management.contextPath`. Also, it is always good to collect this information from XD admin controller that serves what is defined from `info.build.*` attributes.