Fix gradle to include same version as artifact in generated distribution tarball

Version number is now available to both the application plugin and the maven-publish plugin.

Note that this also changes the Maven artifactId from 'twitter-aurora' to 'aurora-scheduler'.

groupId remains 'com.twitter.aurora' - I imagine we will change this to 'org.apache.aurora'
in combination with a refactor of package names.

Testing Done:
'vagrant up' works

'./gradlew distTar' produces dist/distributions/aurora-scheduler-0.2.0-SNAPSHOT.tar
'./gradlew distZip' produces dist/distributions/aurora-scheduler-0.2.0-SNAPSHOT.zip

'./gradlew publishToMavenLocal' publishes appropriately-named binary and source jars

Bugs closed: AURORA-10

Reviewed at https://reviews.apache.org/r/16257/