OPENNLP-1401 Enhance JavaDoc in opennlp.tools.chunker package

[mawiesne]

Change

• adds missing JavaDoc
• improves existing documentation for clarity
• removes superfluous text
• fixes typos
• adds 'final' modifier where useful and applicable
• adds 'Override' annotation where useful and applicable
• removes deprecated and unused constructor in ChunkerME

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[kinow]

Thank you for improving the javadocs, making variable names more consistent and easier to understand, marking some fields as final, and also fixing typos! 🙏