[cando todo] - default behavior

[dulhaver]

current behavior:

cando todo shows open tasks for everyone
cando todo [user] shows open task for a specific user (which might be you, or anybody else)

desired behavior:

cando todo show open tasks for yourself
cando todo [user] show open tasks for that user (which might be you, or anybody else)
cando todo all show all open tasks

I think it's more often the case that you want to see your own tasks, rather then everybody's, so default (simplest) command should show own tasks