cURL does not honour default_socket_timeout

SabreDAV uses cURL for the requests and as this does not honour
default_socket_timeout, setting it is useless and confusing as
people will expect the request to timeout faster than it actually
will do.

One has to use
 curl_setopt($curl, CURLOPT_TIMEOUT, x)
or
 curl_setopt($curl, CURLOPT_CONNECTTIMEOUT, x)
but there is currently no way to make SabreDAV pass this to cURL.

add blacklist to txt preview backend

* owncloud/text_preview_blacklist:
  rename variable in testIsTransparent
  rename testTxtBlacklist to txtBlacklist
  move fileView object initialization to testIsTransparent
  use dataProvider for txt blacklist test
  add test for txt blacklist
  add test data for cal and contact preview
  add blacklist to txt preview backend

handle error situation of rename proper

followup of #4032 - makes the settings-button bigger...

followup of #4032 - makes the settings-button bigger and adds again padding at bottom of app-navigation

Base defaultavatar text on displayname

Fix #4876

phpunit.xml: Port code coverage excludes from autotest to dist.

add initial search in shared files

prelogin apps have to be loaded within setupBackend() otherwise required...

run unit tests for apps as well

manager checkPassword now returns User object, adjust internal user clas...

check only permission from link-share to decide if public upload is enabled or disabled

check if key exists before reading it

Make it possible to have a different color than the username for placeholder

collect coverage for all databases again - ci.owncloud.org has more RAM ...

User: move checkPassword from User to Manager to not break API