When adding and instrument to a score with a pickup bar (anacrusis), set the displayed duration to the pickup length and not a full measure rest
fix 6055 - add Ctrl+Shift+0 as command to convert measures containing only rests into full measure rests, even if they are pickup measures
fix 6055 : when setting the measure length, unless the length is equal to the current time signature
some small fixes and debug in DownloadUtils
Merge pull request #704 from emeraldimp/pickupBugfix

When adding and instrument to a score with a pickup bar (anacrusis), set...
change default shortcut for fullmeasure rest to Ctrl + Shift + Del