Use maven-bundle-plugin directly

This simplifies configuration and is also required to workaround
incompatibility between mavenarchiver plugin and plexus-archiver-2.1.
See https://github.com/tesla/m2eclipse-extras/issues/10
Remove explicit scopes

They are managed in parent so no need to define them explicitly here.
Remove instructions that cause warning

[WARNING] Bundle org.assertj:assertj-core:bundle:1.2.0-SNAPSHOT :
Instructions in Export-Package that are never used: \.
Classpath: Jar:.
Merge pull request #51 from ash2k/pom-cleanup

Pom cleanup