Don't run (nonexistent) partest tests (crashes sbt)

Sbt crash: https://github.com/sbt/sbt/commit/18bc8423b5#commitcomment-3901872
Log: https://scala-webapps.epfl.ch/jenkins/view/pr-validators/job/pr-scala-integrate-partest/892/console
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
Integrate against partest v1.0-RC4

TODO: propagate versions.properties and parse partest version from there, derive tag
crossScalaVersions has no effect -- not setting

Show scala-instance after all relevant settings are set
No need to detect the sbt "boot version".

Overall, the integration script should do less detecting and more setting.
Let's refactor all the builds involved so that this script becomes much,
much, much simpler. How about introducing variables in the builds wherever
necessary, instead of these elaborate sequences of sbt commands,
and maverick search/replace missions.
Quiet the maven
Make sure the ide build has enough memory
Repo HEADs to integrate dependen on scala version
Rewire module dependencies using SCALA_BINARY_VERSION (if set)
test dependency suppression for sbinary
use my repos