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


akretion/openerp-server,akretion/openerp-server,akretion/openerp-server