Adding constant for line.separator and friends

[Alan Bateman]

Ulf Zibis wrote:
>
>> It's also worth pointing out that FileSystem already defines a 
>> getSeparator method.
>
> Oops, I've overseen this too, but wondering that getPathSeparator is 
> missing there.
It's debatable if this would be right or even useful because it extends 
the notion of PATH to all providers. I'm not saying that's a bad thing 
but rather it not might not make sense everywhere. I suspect a list of 
URIs with an agreed delimiter is probably a lot more useful.

-Alan.