delete all children's previews when deleting a folder

add phpdoc
Testcase base class
Do not use uniqid in Group and User tests as it is not unique on windows
Test LargeFileHelperGetFileSize also with ascii only characters

And skip the UTF8 names on Windows as they are not supported
Windows does not support CHMOD, therefor we can not test not writable folders
Add \OC\App\Manager to handle enabling/disabling apps
Skip some more tests on Windows which just can not work at all
Fix single run of encryption tests and usages of uniqid() and fopen()
Correctly close handle of directory when listing certificates
Make it possible to cleanPath() absolute Windows paths
Fix Files\Storage\Home::testRoot()
Correctly refresh the apps list after removing the mock
Correctly restore previous root mount point after testing
Remove unused code

We don't support direct updates from older ownCloud versions except the previous one therefore this code is unused and can be removed.
Move CSRF check
Because we're closing the session now before controllers are executed there are cases where we cannot write the session.
Merge pull request #12031 from owncloud/app-manager

Add \OC\App\Manager to handle enabling/disabling apps
Add sabredav plugin to check if a user has access to an app
Merge pull request #12218 from owncloud/issue/10991-fixes

Issue/10991 Make unit tests pass on windows
Merge pull request #11741 from owncloud/delete_all_children_preview_2

delete all children's previews when deleting a folder
Refactor tests to use a dataProvider method