* Added null check for last password change date. If that is null, use user date creation to check for password expiration.
* Added nullable date checks in AccountController ChangeExpiredPassword action too.
* Added checks on taxonomyId validity (it needs to be > 0) before executing queries that would return no result.
* Added id check on GetTaxonomy(int id) functions.
* Added id check on GetTerm(int id)
* Removed id check on GetTaxonomy(int) function to avoid changing previous behaviour.
* Returned "Array.Empty" instead of "new List" where an empty list must be returned.
* Added statuses management instead of notifier when catching file not found exception
# Conflicts:
# src/Orchard.Web/Modules/Orchard.MediaLibrary/Controllers/ClientStorageController.cs
* Visual studio automatic code formatting.
* Added password history management to back office user password edit and made it working via IUserEventHandler calls.
* Added "password" parameter to "ChangedPassword" call.
Andrea Piovanelli