Introduces the basic password authentication mechanism, along with a
mechanism based on ownCloud credentials stored in the user session.
Change to lib/private is an extension of PermissionsMask, as
isSharable() override was missing.
Session credentials auth mechanism now disables sharing on applied
storages, as credentials will not be available.
Jörn Friedrich Dreyer
Robin McCorkell
Jenkins for ownCloud
Morris Jobke
Robin Appelman