Add a way to check if Path points to a link

[vdshb]

I can see Path.isDirectory and Path.isRegularFile but I can't see a way to detect symbolic link.

This is a proposal to add Path.isSymbolicLink and Path.isHardLink properties which detect whether Path points into symbolic/hard link or not.

[vdshb]

I'll put it here as a reference: https://docs.oracle.com/javase/tutorial/essential/io/links.html

I'm not an expert in this field, so maybe Path.isHardLink is harder/impossible to implement. In this case, this proposal is only about Path.isSymbolicLink.

[fzhinkin]

Similar issue: #330