Changed autocorrection options in oh-my-zsh

Added more granularity to correction options:
- Disable correction at all
- Disable correcting arguments (and aliasing commands 'nocorrect'-ed)
Add return codes to agnoster theme

This adds the ability to show the return code of every process in a pipe chain,
as long as at least one of them returns a value other than 0.
There is the option to disable this behaviour as well.
Merged from robbyrussell/oh-my-zsh/pull/2573 (by @diogovk)
Show literal command in title instead of unaliased