[DEV] open new 1.5 development branch

This new branch is based on 1.4.6, which 1.5-dev0 is 100% equivalent to.
The roadmap has been updated.
diff --git a/VERDATE b/VERDATE
index ad186d8..bf310d7 100644
--- a/VERDATE
+++ b/VERDATE
@@ -1 +1 @@
-2010/05/16
+2010/05/20