addSyncedPlugin/addSyncedTheme should delete files

[bravadomizzou]

Recently did a deployment and it broke the website because it left files in that were deleted (model files, component files) It should delete the files as one would expect, or have some flag.

[lynnbgriffith]

You can add the delete() flag on the related rsync step. Do --list-steps to see the steps in your script and adjust as needed. I've discussed changing the default with Jared. The blocker on that is adding a check that warns when files on the remote will be deleted.