PythonQt Code

- removed warnings
- fixed some memory leaks (only on cleanup)
- fixed bad QString usage as %s argument
- added PythonQtQFileImporter, which implements a default importer using QFile
- added PythonQt::self()->installDefaultImporter() to enable the new default importer
- modified example to make use of new importer
- removed ugly goto, which was copied from original zip import