add LinkOwner interface #342

[jxsl13]

Adds the ability to change ownership of symlinks.

read the issue at: #342

The use case is described in the issue as well.

Extends the Symlinker interface, requires more methods to be implemented. Might be a breaking change in that regard which could be resolved by removing the LinkOwner interface from the Symlinker interface.

The change may be less severe due to most structs that implement parts of the symlinker interface have also been updated.

Feedback required :)