Revert "Move to Scala OSGi bundles."

Partial revert, kept the Java 1.6 dependency definition.

This reverts commit e6f68f08fa79c00ab019ea0523eca667d14f3b0d.
Revert "Fixed source compatibility with latest Scala IDE master"

This reverts commit 9e83a5f42b12315ef96871d5d04624560030b799.
Adds a local impletation of the version checker

It is not available in the test tools from Scala IDE 3.0.x.