Reduce warning messages in unit tests.

We get a warning on any attempt to use anything that may be affected by DeveloperSettings, because DeveloperSetting tries to use ConfigurationProperties to find its properties file. We could avoid this by requiring the use of a ConfigurationPropertiesStub, but it seems to make more sense to routinely create a DeveloperSettingsStub on each ServletContextStub.
Merge branch 'maint-rel-1.6' into develop