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 2590709..2497546 100644
--- a/project.config
+++ b/project.config
@@ -97,3 +97,5 @@
 	header = to
 	type = submitted_changes
 	filter = -project:scratch
+[access "refs/for/*"]
+	addPatchSet = group Registered Users