...to not suggest invalid file paths.

  * Use id() for methods returning a string used to represent
    some type of object.
  * Use displayName() for strings that are meant to be user
    visible.
  * Quieten some warnings while touching the files anyway.
  * Move Factories to their products in the plugins where that
    was not done before.

Reviewed-by: dt

- Introduce project directory and "use" flag to file manager, use that
  in new item dialog
- Add configuration under Project settings, rename it to "General"
- Make wizards create project names as "untitled1.."
- Remove modules page from Qt application wizards (parametrizable)
- Give Utils::ProjectIntroPage a "Set as default location" toggle.
- Introduce wizard dialog base classes for handling that.
- Introduce notion of "last visited directory to file manager" for
  open and non-project wizards, route open through file manager.
- Clean out QmlAppWizard

Task-number: QTCREATORBUG-333
Rubber-stamped-by: con <qtc-committer@nokia.com>