Added ability to apply patch to existing list inplace

[andre161292]

Motivation

I'm using java-diff-utils to update lists in JPA models from a DTOs. As Hibernate uses proxies and records any removal/add/swap, but has it's problems when using clear/addAll, this is the only option to make patching my lists work.

In older versions i accessed AbstractDelta's applyTo directly, but that fell away when it was made hidden in 3075742.

Changes

I added a the methods applyToExisting and it's opposite restoreToExisting to Patch, to make it possible to update lists in-place and updated JavaDoc accordingly.

Minor improvements

I corrected a typo in the method-name verifyAntApplyTo -> verifyAndApplyTo

[wumpz]

But as I understand it, you did not add but change the existing behaviour, right?

[andre161292]

But as I understand it, you did not add but change the existing behaviour, right?

No, i didn't change the existing behavior. I extracted the core functionality to make it accessible from the outside, that's why it looks changed at first.