WIP: Lucene upgrade

[steffenvan]

Working branch for a Lucene upgrade. Plans to officially upgrade it has been halted. So this can serve as a starting point in the future.

Version 5:

• [x] 5.5.0
• [x] 5.5.1
• [x] 5.5.2
• [x] 5.5.3
• [x] 5.5.4
• [x] 5.5.5

Version 6 (TBD):

• [ ] 6.0.0
• [ ] 6.0.1
• [ ] 6.1.0
• [ ] 6.2.0
• [ ] 6.2.1
• [ ] 6.3.0
• [ ] 6.4.0
• [ ] 6.4.1
• [ ] 6.4.2
• [ ] 6.5.0
• [ ] 6.5.1
• [ ] 6.6.0
• [ ] 6.6.1
• [ ] 6.6.2
• [ ] 6.6.3
• [ ] 6.6.4
• [ ] 6.6.5
• [ ] 6.6.6

Version 7 (TBD)

• [ ] 7.0.0
• [ ] 7.0.1
• [ ] 7.1.0
• [ ] 7.2.0
• [ ] 7.2.1
• [ ] 7.3.0
• [ ] 7.3.1
• [ ] 7.4.0
• [ ] 7.5.0
• [ ] 7.6.0
• [ ] 7.7.0
• [ ] 7.7.1
• [ ] 7.7.2
• [ ] 7.7.3