[FIX JENKINS-22867] Fix localization and relative links.

@jglick's b36b0d60da7a8b5ed62a4c7a0ea05fe518015e6d broke localization of the Maven builder help, while only implementing its goal – use of absolute link target – in English. This commit fixes the Jelly localization by switching to properties files, and implements the absolute link in all localizations.

As I'm unfamiliar with most of the languages, there may be missing spaces in these localized texts.

Using `&#123;` instead of `{` with special meaning in `java.text.MessageFormat`. Found out about `'{'` too late to care.