Make `maven` run in batch mode (remove hundreds of lines of download progress).
Correctly retrieve `sbt.version` from pom.xml.

This should fix failures like [1508](https://scala-webapps.epfl.ch/jenkins/view/pr-validators/job/pr-scala-integrate-ide/1508/consoleFull)
Merge pull request #20 from dragos/fix/ide-sbt-version-failures

Correctly retrieve ${sbt.version} from pom.xml