Remove old way of configuring cloudooo preference

This is what we discussed in https://lab.nexedi.com/nexedi/erp5/merge_requests/146

All old style preference accessors are removed and a compatibility layer is introduced in runUnitTest so that the configuration for tests ( Products.ERP5Type.tests.ERP5TypeTestCase. _getConversionServerDict already have url configured even if runUnitTest is called wih host and port)