Remove Upload module from core.

With the adding of the fieldapi to core, and that there are some really good file uploading modules in contrib, I recommend that we now remove the upload module in favor of contrib modules like filefield which would makes full use of the fieldapi and allow file fields to be added to any first class object.

I have not created a patch yet, as it is quite simple, but I was just thinking of generating some discussion around this be I create a patch.