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
eliminate OC_Template::printErrorPage in database classes, fixes #12182
Show warning when invalid user was passed

Sometimes there are bugs that cause setupFS() to be called for
non-existing users. Instead of failing hard and breaking the instance,
this fix simply logs a warning.
errors are already logged
do not output DB information, and do not set header
[tx-robot] updated from transifex
[tx-robot] updated from transifex
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 phpass and migrate to new Hasher interface

This PR removes phpass and migrates to the new Hasher interface.

Please notice that due to https://github.com/owncloud/core/issues/10671 old hashes are not updated but the hashes are backwards compatible so this shouldn't hurt.
Once the sharing classes have a possibility to update the passwords of single shares those methods should be used within the newHash if block.