Switched completion to be case-insensitive by default

Quite a few people seem to prefer this and it is the default in Eclipse
and MSVC.

This applies to both C++ and QML completion.

Task-number: QTCREATORBUG-1474

src/plugins/texteditor/completionsettings.cpp

@@ -40,7 +40,7 @@ static const char * const spaceAfterFunctionNameKey = "SpaceAfterFunctionName";
 using namespace TextEditor;
 
 CompletionSettings::CompletionSettings()
-    : m_caseSensitivity(FirstLetterCaseSensitive)
+    : m_caseSensitivity(CaseInsensitive)
     , m_autoInsertBrackets(true)
     , m_partiallyComplete(true)
     , m_spaceAfterFunctionName(false)