add target="_blank" to href in setupcheck

Make a modifiable copy of the webdav properties in JS file list

Plugins can extend _getWebdavProperties to add custom properties.
These should not be added to the original properties list, so now the
FileList makes a copy of the array.

Adding integration tests for CalDAV

Add error logging to federation handshake

Restore DB connection after failure

In case of failure, PHPUnit seems to skip `tearDown`, so any useful
assertion messages cannot be shown because `tearDownAfterClass` is
throwing an error because of database usage.

This commit makes sure we also restore the database in
`tearDownAfterClass` to prevent the data root restoration to fail

Restructure travis tests

Fix carddav sharing plugin + adding unit tests

Do not delete background jobs, in case an exception occured

Use new APCu API

Update README.md

[3rdparty] Bump symfony/process to 2.8.0

This one is available since APCu 4.0, since we require APCu 4.0.6 this works fine. Also it brings us PHP 7 compatibility and thus fixes https://github.com/owncloud/core/issues/21095

-Added Facebook into "Get in touch"-section
-Improved Emojis on "Get in touch"-section
-Added Support Information

Allow background jobs to be service names for DI

Use OCP\Util::getVersion instead of the internal private implementation

[3rdparty] Bump symfony/routing to 2.8.0

Remove deprecated OC_Helper mimetype functions

Cleanup OC_Config mess

OC_Helper::makeURLAbsolute is not used anymore

This approach is not valid anymore. It initially was added for jobs
of non existing apps. But jobs of non-existing apps can not be created
so they will never be executed and so this call just catches other
cases which were not intended.

This reverts commit 4f4ad724.