require confirmation before deleteing files in the gui
- added confirmation to Project removeFile/removeFiles (prob shouldn't be done in Project.js)
- Util.confirm now returns a promise, Project.revert updated
move file delete confirmations into FileTreeFrame
update gui remove_files test to exercise confirmation dialog
change private methods to use local project reference in FileTreeFrame
Merge pull request #1510 from swryan/filetree

gui - require confirmation before deleting files