Remove language from set_trytond

This parameter is no more used.

issue4403
review11701002

--HG--
extra : rebase_source : b74e095b08af66d220896f23d30e411cad65a587
Fix __repr__ of config

- Wrong argument number for TrytondConfig
- Use repr for argument

issue4395
review14761002
Add unittest for repr of TrytondConfig

issue4395
review14761002