Improve UX/UI for adding letter-sound correspondences

[nya-elimu]

Simplify the process of adding letter-to-sound mappings when creating/editing a word.

• Rename to LetterSoundCorrespondence webapp#1373
• Add LetterSoundCorrespondence contribution event webapp#1372
• Add SoundContributionEvent webapp#1496
• Add LetterSoundCorrespondencePeerReviewEvent webapp#1484
• Fix problem with adding letter-sound correspondence webapp#1517
• List the letter-sound correspondences where a letter is used webapp#1701
• List the usages of a letter-sound correspondence webapp#1479
• List the letter-sound correspondences where a sound is used webapp#1518
• Make letters and sounds clickable when creating/editing correspondence webapp#1521
• Make diacritics clickable in the list of letter-sound correspondences webapp#1196
• Fix incorrect URL for peer-reviewing letter-sound correspondences webapp#1524
• Play sound(s) each time a letter-sound correspondence is added to a word webapp#1374
• Replace true/false with "Yes"/"No" in the Diacritics column of a Letter webapp#1522
• Remove deprecated text property from Word webapp#1769