make sure that only one process can enter the migration mode
use constants for different migration status
adapt test to the code changes
use number of manipulated rows as idicator if it was possible to enter the migration mode

Conflicts:

	apps/files_encryption/lib/util.php
fix typo in var name
add comment to explain the helper function
fix for autoloader while user logged in and system is in maintenance

Conflicts:

	apps/files_encryption/appinfo/app.php
use legacyDecrypt to decrypt key file like the previous files_encryption
fix re-encrypt legacy files

Conflicts:

	apps/files_encryption/lib/util.php
fix legacy key in until test
normalize path to prevent following split to fail
cleanup unused method legacyKeyRecryptKeyfile
check if the decrypted private key is valid on login and on read/write files
allow the user to login but do not allow upload and show error message on the web

Conflicts:

	apps/files_encryption/appinfo/app.php
code optimized and cleaned up unused vars
introduce decryptPrivateKey() method which also checks if the result is a valid private key to avoid additional checks on various places

Conflicts:

	apps/files_encryption/lib/session.php
control files are no longer needed, remove them from the tests
$session->setPrivateKey expects only one parameter
let user update private key password in case it was changed from outside, e.g. external auth back-ends
added test for decryptPrivateKey()