qt5webkit: cleaunup cookiejar

remove redunancy
qt5webkit: enable custom (storage) paths in WK2

WK2 defaults to QStandardPaths which might not result in appropriate locations
qt5webkit: improve custom (storage) paths in WK2

Improved implementation
qt5webkit: updated asserts

cleanup, stronger asserts and avoid possible assert on StorageType update
qt5webkit: clean-up QtWebCustomPaths

Remove Assignment operator, copy constructor, and PersistentStorage from QtWebPathType
Merge pull request #6 from Metrological/cookiejar

Cookiejar