Bring markup for mavenCoordinates in sync with maven

While adding new libraries by reference to Maven central in libraries/plugin.xml, it occurred to me that

```

```

is unnecessarily distinct from actual maven pom.xml markup. This might better be simply

```

javax.servlet
servlet-api
2.5

```

If nothing else, this enables us to add new libraries with more copy-pasta and less error-prone manual typing. I did encounter on bug (mixed up groupId and artifactID) that cost me a few minutes here.