Various cleanups, fixes and improvements

Squashed all commits that were meejah's between
30d68fb499f300a393fa0ced5980229f4bb6efda
and
33c268ed3a8c63a809f4403e307ecc13d848b1ab
On the branch meejah:1382.markberger-rewrite-rebase.6 as
per review

src/allmydata/client.py

@@ -655,6 +655,6 @@ class Client(node.Node, pollmixin.PollMixin):
         return self.nodemaker.create_mutable_file(contents, keysize,
                                                   version=version)
 
-    def upload(self, uploadable):
+    def upload(self, uploadable, reactor=None):
         uploader = self.getServiceNamed("uploader")
-        return uploader.upload(uploadable)
+        return uploader.upload(uploadable, reactor=reactor)