New code assist API

This is a re-work of our completion engine. Primary goals are:

- Allow the computation to run in a separate thread so the GUI is not locked.
- Support a model-based approach. QStrings are still needed (filtering, etc), but
internal structures are free to use more efficient representations.
- Unifiy all kinds of *assist* into a more reusable and extensible framework.
- Remove unnecessary dependencies on the text editor so we have more generic
and easily "plugable" components (still things to be resolved).

src/plugins/qmljseditor/qmljscomponentfromobjectdef.h

@@ -41,7 +41,8 @@ namespace Internal {
 class ComponentFromObjectDef: public QmlJSQuickFixFactory
 {
 public:
-    virtual QList<QmlJSQuickFixOperation::Ptr> match(const QmlJSQuickFixState &state);
+    virtual QList<QmlJSQuickFixOperation::Ptr> match(
+        const QSharedPointer<const QmlJSQuickFixAssistInterface> &interface);
 };
 
 } // namespace Internal