Support indepotent behavior for add / remove

[EugenMayer]

It would be great to be able to add and remove entries (using a flag like --force) where the behavior does not break

• add is used even though the item already exists
• remove is used even though the item is already missing

Right now i use this for add:

storm add $NAME $USER@$HOST:$PORT 2>&1 | grep -v error || storm edit "$NAME" $USER@$HOST:$PORT

and this for remove

storm delete $NAME > /dev/null 2>&1 || true

This is important for automations with ansible/homemaker and others, where you setup shared / common ssh aliases and things like that.

Thanks!