Allow returning Self instead of Option<Self> for Prep methods that always go to Ready

[uazu]

Option provides a From implementation for T such that Option::from(val) on both T and Option<T> will result in Option<T>. So all Prep calls could be wrapped in Option::from(...) to handle both. This needs testing to check that it causes no issues. It also requires some consideration to be sure that it won't confuse coders who might forget that there's a way to delay moving to the Ready state.