rename 'save' to reduce confusion with cloning

an extremely common mistake is to attempt to clone some entity, but mistakenly click on "save" without actually clicking on one of the clone buttons.

this mistake is done both by new and experienced users, so we could try to help them instead of blaming them

the suggestion is to change "save" in hosts, items etc "add" or "update", same as is done in web scenario steps, action operations and some other places