WIP: Reworked bottleneck import: - all available bottlenecks from the service are loaded (including historic data) - kudos to Tom Gottfried - Bottlenecks which are identical to an exiting (non staged) one are recognized as "unchanged" and ignored. - All remaining Bottlenecks are inserted into Staging area - On "staging done" all existing bottlenecks with conflicting (bottleneck_id,validity) are deleted (replaced by the new bottlenecks). Known Issues: - Sometimes the identification of unchanged bottlenecks does not work, needs debugging. - The front end does not handle historic data correctly (we need to define what "correctly" should be). - Save points should be used to distinguish ignored errors from fatal ones.