QmlJS: Split Context and ScopeChain.

Context is created by Link and has information about imports
for all Documents in a Snapshot.

ScopeChain represents how lookup is done at a specific place in
a Document.

Change-Id: I874102d57bbaf1a497fa3f27633bed6ee75dcf10
Reviewed-on: http://codereview.qt.nokia.com/1694
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@nokia.com>

src/plugins/qmljseditor/qmljseditor.cpp

@@ -1260,7 +1260,7 @@ TextEditor::BaseTextEditorWidget::Link QmlJSTextEditorWidget::findLinkAt(const Q
     }
 
     LookupContext::Ptr lookupContext = semanticInfo.lookupContext(semanticInfo.rangePath(cursorPosition));
-    Evaluate evaluator(lookupContext->context());
+    Evaluate evaluator(&lookupContext->scopeChain());
     const Interpreter::Value *value = evaluator.reference(node);
 
     QString fileName;