[Tizen/Desktop] Re-organize storage partition management

This patch removes storage partition cleanup logic from Application
Storage and Package Installer making them completely independent
from browser content API layer. Hence now both of them can be used
outside the browser process (e.g. from 'xwalkctl').

The Application Storage implementation is now much simpler which is
very important as we have plans to create an alternative Application
Storage implementation for Tizen, based on the platform 'app_info.db'.