@deprecated messages for \OCP\Config and \OCP\AppConfig
use old methods and redirect in deprecated methods
migrate AllConfig app related methods to DI
migrate \OC\AllConfig to \OCP\IConfig
introduce deleteAllUserValues
drop unused isDebugMode and setDebugMode of OC_Config
fix base.php for not installed systems
re-init the database connection after autoconfig is loaded - otherwise SQLite will break
Refactoring of OC_Preferences to AllConfig

* keep old static methods - mapped to new ones and deprecated
* removed deleteApp, getUsers, getApps, getUsersForValue because they
  are unused
* make AllConfig unit tests more robust against not cleaned up environments
introduce preCondition for setUserValue to provide atomic check-and-update
Workaround to fix the too early init dilemma

* this needs to be properly fixed by a proper organisation of the base.php
* introduced fixDIInit() in AllConfig that moves the injection
  of DatabaseConnection to a later point in time
* problems mostly because of the autoconfig setup
reduce OC_Preferences and OC_Config usage

* files_encryption
* files_versions
* files_trashbin
* tests
* status.php
* core