Add <remote project-name="..."> attribute within projects

By setting a project-name on a remote nested within a project forks
of a project like the Linux kernel can be easily handled by fetching
all relevant forks into the same client side project under different
remote names.  Developers can create branches off different remotes
using `git checkout --track -b $myname $remote/$branch` and later
`repo upload` automatically redirects to the proper fork project
in the code review server.

Signed-off-by: Shawn O. Pearce <sop@google.com>

project.py

@@ -904,7 +904,9 @@ class Project(object):
       remote = self.GetRemote(r.name)
       remote.url = r.fetchUrl
       remote.review = r.reviewUrl
-      if remote.projectname is None:
+      if r.projectName:
+        remote.projectname = r.projectName
+      elif remote.projectname is None:
         remote.projectname = self.name
       remote.ResetFetch()
       remote.Save()