Progress on #3624 - factor out some logic into new file
_hierarchyCommand.js, add support for mobile ListItem handling to
RemoveCommand.js (had been missing). Still need to study
ReparentCommand.js and look for other opportunities to refactor code.
Merge branch 'master' into 3624-CleanupCommands
Fixes #3624 - make sure RemoveCommand And ReparentCommand deal with
special quirks of mobile lists. Factor out a commonly used subroutine.