[FIX] config: when assigning new value, ensure that value are correctly type checked

This make configmanager stronger about config params values (if we need to enforce
  them as int, float, ...). Helping gunicorn user's to not set wrong value, like:

     conf['cpu_time_limit'] = '180'

  In that case, type checker will gracefully convert it to interger.

bzr revid: xal@openerp.com-20120523125354-jr6lgpecjyqrmaz3

openerp/tools/config.py

@@ -624,6 +624,8 @@ class configmanager(object):
 
     def __setitem__(self, key, value):
         self.options[key] = value
+        if isinstance(self.options[key], basestring) and self.casts[key].type in optparse.Option.TYPE_CHECKER:
+            self.options[key] = optparse.Option.TYPE_CHECKER[self.casts[key].type](self.casts[key], key, self.options[key])
 
     def __getitem__(self, key):
         return self.options[key]