add scala nature

this requies cos' fork of sbt-maven-plugin
it is hardcoded for os x for now
add dependency graph printing to sbt
remove .project from k-core

we can have the external tool builder commited, but having also the .project creates one extra item to ignore manually, as it remains tracked
Merge branch 'feature/scala-nature' into develop
Merge branch 'hotfix/remove-dot-project' into develop