Make Detailed completion:Never option work

The <default> element is outside of (not nested in) the <entry> element, and therefore does not work correctly. When the user chooses the "Never" item in the Detailed completion combobox on the Language Support tab of the Configure - KDevelop dialog, KConfig believes that the default value is selected and removes the completionDetail entry from kdeveloprc. Then KConfigGroup::readEntry() returns its second argument in CompletionSettings::completionLevel(), which is MinimalWhenAutomatic ("When Invoked Manually" in the UI). And thus the "Never" choice works just like the "When Invoked Manually" choice.