Add releng component for building with buckminster

This enables mirroring of the p2.site using p2 actions from buckminster
This file also contians extra dependencies needed to build the bundles in this repo
Updates bundle versions to 2.6.1
Feature version set to 2.6.1
Changes scope to include instance, configuration and default

Solves bug 3499
Remove DefaultScope form search contexts

DefaultScope is automatically added to ScopedPreferenceStore's search contexts
Fixed the predictWithModelWithLabel(.., .., List<>) method
Merge pull request #18 from egonw/bug/predictWithLabelFix

Bug/predict with label fix
Merge branch '2.6.1' into develop