Enforce compatible core version

see: https://www.openproject.org/work_packages/13947
Merge pull request #104 from finnlabs/fix/enforce_right_core_version

Enforce compatible core version
Add spec
Fix missing story points
Merge pull request #107 from finnlabs/hotfix/show_story_points_in_wp_show
Adapt version to corresponding OpenProject core version
Update stable to v3.0.11