Assign default add patch set permission on refs/for/*

By default each user should be able to add patch sets on all open changes.
We have created a new permission to lock changes, such that only
the change owner or a specific group can add new patchsets to exisitng
changes.

project.config

diff --git a/project.config b/project.config
index ab42c75..8d16587 100644
--- a/project.config
+++ b/project.config
@@ -70,3 +70,5 @@
 	agreementUrl = static/cla.html
 	autoVerify = group Akaros-CLA-Accepted
 	accepted = group Akaros-CLA-Accepted
+[access "refs/for/*"]
+	addPatchSet = group Registered Users