clarify upload design

Things that are missing from this explanation on paths:

* These are the paths we use, they are or aren't "baked" into the API? I.e, we suggest these, but you can choose your own (see XXX.scala for details) 
* The relationship between DB, table name, "domain" and other parts of the path structure aren't clear
* This notion of "raw" Vs "conformed" Vs "Generated" and what that means at that level of folder structure...