[feature request] Allow user to select/deselect default parameters

[Oliver Huf]

I for one use rsync almost exclusively in a way to ignore "deletes".
Whenever I add a new task I have to make sure "--delete" is removed from the list of default parameters.
Request: please add a way to set the default parameters for a new task (e.g. remove --delete by default and allow to add optionally later in the "parameters" dialog) .