Validate whether xrefs and footnotes referenced from verse text exist
Merge branch 'feature/footnote_xref_validation' into develop
Merge commit '29bff18d2a795bba85f634d340b375618a1910ef' into develop
Update "cannot play song" button
Remove unused DownloadThread in AddonManager
Remove fade out animation on devotion download status
Version config can now be updated online.