[FIX] base: help message of an action as html

Convert help field on an ir.action to html as it was already used do display
html messages.
Converting it to html allows to benefit from changes made at 75140d7e for better
translation of help message.

openerp/addons/base/ir/ir_actions.py

@@ -35,7 +35,7 @@ class actions(osv.osv):
         'type': fields.char('Action Type', required=True),
         'usage': fields.char('Action Usage'),
         'xml_id': fields.function(osv.osv.get_external_id, type='char', string="External ID"),
-        'help': fields.text('Action description',
+        'help': fields.html('Action description',
             help='Optional help text for the users with a description of the target view, such as its usage and purpose.',
             translate=True),
     }