Rename createFile/createDirectory to createNode/createCollection

[PVince81]

It is more and more common (or at least in ownCloud) to use Sabre nodes for other things than files and folders. So eventually it might make sense to revamp the ICollection interface:

• rename createFile to createNode
• rename createDirectory to createCollection

@evert

[evert]

This is a good idea. The Directory/Collection thing has been bugging me forever. Perhaps 4.0 is a good time to finally do this.

I'd keep createFile though, because file to us means something that has a body and can have a PUT or a GET request, so this terminology is still everywhere (unlike Directory).