Issue 4763: Web: Review GSoC page

Issue 4763: Web: Review GSoC page

Web/GSoC: Review list introduction
Web/GSoC: Review ScholarLY project description
Web/GSoC: Review Grace Notes project description
Web/GSoC: Review MusicXML project description
Web/GSoC: Review Slurs project description
Web/GSoC: Review Glyphs project description
Web/GSoC: Review Beaming project description
Web/GSoC: Review Compilation project description
Web/GSoC: Sort projects by mentor availability
Web/GSoC: Insert Spanner-per-Voice project suggestion
Web/GSoC: Incorporate suggestions by Paul's review
Web/GSoC: Add "Chord structure" project