This should allow us to be able to remove a stage from a dvcfile,
(if it's a single stage file, it removes it), and make us able to
delete the overwrite the stage on run as well.
This commit:
* changes `run` `--overwrite-dvcfile` flag to `--overwrite`
* removes prompt in `run` for overwrite and fails hard
* changes `remove`: now it by default removes stage entry and unprotect outs
* `remove` has `--outs` to remove outputs instead of unprotecting them