Just the declaring member isn't enough.

Instead of only maintaining a flat list of scopes, actually store the
global, component chain, root object, scope object, function, id and js
scopes separately.

* Add SemanticHighlighter to QmlJSTextEditor to update the semantic info
  in a background thread.
* Add QmlJS::Check to run semantic checks on qml and js documents.
* Add a check for incorrect property names.
* Fix hoverhandler to show tool tips from extra selections over help
  tooltips.

* For JS files: Add each Qml component that sources the file in a Script
  tag to the scope chain.
* For Qml components: Add each component that instantiates the component
  to the scope chain.
* Generate the full list of documents required for completion in a
  given file. Previously, files that included the file were missing.

There is no reason to store the Bind object in a QSharedPointer because the `binder' has the same
lifetime of its document.

Done-with: ckamm

* Support for lookup JS vs Qml
* Bind global variables.

Done-with: ckamm

Done-with: Roberto

Done with ckamm

Reviewed-by: Roberto Raggi <roberto.raggi@nokia.com>