Add function add_xmlid to OpenUpgrade API
Take into account the remarks of Stefan :
- noupdate defaults to False
- don't use %d in pscopg
- don't update the existing entry in ir_model_data
Use logged_query() instead of cr.execute()
PEP8 stuff
Merge pull request #23 from alexis-via/add-xmlid

[ADD] Add function add_xmlid to OpenUpgrade API