DragnDrop Upload text style

The 8px margin was uggly.
Reenable file proxy when renaming between mount points

When moving a folder into another mount point, $renamedFiles is empty
because that goes over a different mechanism.

In such case, this fix makes sure that the file proxy is reenable to
avoid breaking the subsequent files that are being moved.
Added extra check to avoid deleting key folders

Whenever a delete operation is called twice in a row, it could happen
that the first call already deleted the file.

The second call would return an empty $ownerPath because the file does
not exist. That empty $ownerPath would run the key deletion operation on
the wrong path.

This fix adds checks in many places to make sure we don't use $ownerPath
when it's empty or null.
add seek and tell to streamwrapper test
return boolean in OC::stream_seek
return boolean in Ciose::stream_seek
in quota wrapper use === instead of ! for better readability and as in other wrappers
show upgrade errors as error in the console and report back that the upgrade process failed if it did
remove bootstrapping - occ can by definition only be executed if ownCloud is installed - base.php is required earlier already
no loner use deprecated class \OC_Config
Fix autotest.sh for whitespace in paths
WebDAV now throws 403 when deletion did not work

Assume a permission issue whenever a file could not be deleted.

This is because some storages are not able to return permissions, so a
permission denied situation can only be triggered during direct
deletion.
send browsers timezone back tp the server on login
date printed in the admin section regarding last execution time is already displayed in the users timezone - no need to append UTC
enhance formatDate function to accept an optional argument containing the time zone
first check if a private key exists, if not it is always a recovery szenario
Add a configuration switch for enabled preview mimetypes
fixing directory seperators
Merge pull request #11212 from owncloud/occ-catching-errors

Occ catching errors
Merge pull request #11204 from owncloud/fix_oc_stream_seek

Fix oc stream seek