QmlJS: Fix semantic and non-semantic QML error reporting.

The QML snapshot only ever contains valid Documents; to compile a list
of parser problems we need to get at the invalid documents.

To do that, the model manager now provides a Snapshot with up to date,
but potentially invalid documents. That should also be useful for other
things.

Change-Id: I67892f63771c221bf2fe2c2bf0240a0f4e523227
Reviewed-on: http://codereview.qt.nokia.com/3012
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@nokia.com>

src/libs/qmljs/qmljsdocument.h

@@ -198,7 +198,7 @@ public:
     const_iterator begin() const { return _documents.begin(); }
     const_iterator end() const { return _documents.end(); }
 
-    void insert(const Document::Ptr &document);
+    void insert(const Document::Ptr &document, bool allowInvalid = false);
     void insertLibraryInfo(const QString &path, const LibraryInfo &info);
     void remove(const QString &fileName);