Add new 2 fields

* self.write = False
* self.read = False

so that user can write like 
'name': fields.char('Name', size=128, write=['base.group_admin'], read=['base.group_admin']),
or 
'name': fields.char('Name', size=128, write=['base.group_admin']),
or 
'name': fields.char('Name', size=128, read=['base.group_admin']),
if only write applied read will allow for all users but if readonly is 
applied then same will be applied for the write 

so 'name': fields.char('Name', size=128, read=['base.group_admin']), will work same as 
'name': fields.char('Name', size=128, write=['base.group_admin'], read=['base.group_admin']),

bzr revid: mga@tinyerp.com-d62db1be538eb3bc9599f414092266a9764dd7fb

bin/osv/fields.py

@@ -81,7 +81,8 @@ class _column(object):
 		self.relate =False
 		self._context = context
 		self.group_name = False
-		self.groups = False
+		self.write = False
+		self.read = False
 		self.view_load = 0
 		self.select=select
 		for a in args: