added DeletionRangeILN
new bsz Events implementation

- EventsPreflight broke the pattern too much.
- Events are now filtered on a per ILN basis (since deletions are ILN based).
- Switch to ISIL should be easier with this processing.
- Processing time per ILN depends on the number of records for that ILN,
  e.g. 30s for 0010, 15s for 0020, ...