DragnDrop Upload text style

The 8px margin was uggly.
Do not show exception to the end-user

Log the error instead of potentially leaking sensitive information
replace horizontal rules with whitespace
fix error message template
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
correct delete-icon to icon-delete, fix #11128
correct progress-icon to icon-loading-small
force show the loading icon in list for deletion, not only on hover
Use only lower-case letters

Fixes https://github.com/owncloud/core/issues/11239
Moved WebDAV and internet checks to client side JS

- Added setup checks in JavaScript
- Moved isWebDAVWorking to JS using SetupChecks
- Moved internet connection checks to an ajax call that goes through the
  server
Merge pull request #11241 from owncloud/use-lower-case

Use only lower-case letters
Fix share key finding algorithm in various cases

Instead of inaccurate pattern matching, use the list of users who we
know have access to the file to build the list of share keys.

This covers the following cases:

- Move/copy files into a subfolder within a share
- Unsharing from a user
- Deleting files directlry / moving share keys to trashbin
Merge pull request #11137 from owncloud/enc-pregfix

Fix share key pattern matching
Merge pull request #11234 from owncloud/fix-icon-classes

Fix icon classes, disappeared delete icon
adjust text size and opacity of drag'n'drop upload text style
Merge pull request #11222 from owncloud/store-users-timezone-master

send browsers timezone back tp the server on login
Merge pull request #11109 from owncloud/nstamm-patch-1

DragnDrop Upload text style
fix filepicker home icon being partly hidden, fix #10169