External FTP Storage should request hostname instead of URL

Fix issue #6277

Backport of 658af62
Make google drive client secret and dropbox api secret a password field

Fix issue #5794

Backport of 828985d
Concatenate string in SQL instead of PHP, use doctrine to construct concat expression
An admin should not be able to add remote and public services on its own. This should only be possible programmatically.
This change is due the fact that an admin may not be expected to execute arbitrary code in every environment.
Check whether the Key is set
Check whether the app is set
Security Update: session fixation

Previous version is vulnerable to session fixation attack in some situations, guessing non-apache-module-php5 environment. Regeneration of session id should be done here.
Update user.php to fix duplicate session-duplicate
LDAP: prevent other configuration from being deleted when deleting the first one which has an empty prefix for historical reasons
Add missing slash in URLGenerator::getAbsoluteURL(). Refs. #6840
Test if $url is already prefixed by '/'
Fix "headers are already sent" introduced with #6519

Backport of #7347
LDAP: improve compilation of filters
LDAP: fix and extend tests
Merge pull request #7349 from owncloud/backport-7347

Backport of #7347 to stable6
add unit test for \OC\URLGenerator::getAbsoluteURL to verify #6935
fix sharing unit tests
Updated submodule

Includes XML fixes
fix usersPath and add unit tests
fix test so that it doesn't depend on the array order