Fixes #5775

Previously, the storage statistics were always for the root dir.
This means that the upload button would always show the limit for the
root dir, even when uploading to a shared dir or external storage.

This fix adds a "dir" argument to getstoragestats.php.

After uploading, the quota value wasn't refreshed.
This fix refreshes the quota value after files have been scanned or
uploaded.

calling getstoragestats.php only if a user is logged in because this call requires a user to be logged in

closest will search up the tree

forward port of https://github.com/owncloud/core/pull/5647#discussion-diff-7341163
trust me, I know what I'm doing

Fixes #5534

- show tooltip when violating naming constraints while typing
- when target filename exists on server fallback to dialog to interrupt the users flow because something unexpected went wrong
- fixes #5062
- also fixes some whitespace and codestyle issues in files js
- uses css selector over filterAttr in touched js files

Preview images are now pre-loaded before being set on the file element.

This fixes #5135 and prevents a white space to be displayed while the
thumbnails is being loaded.

give getSelectedFilesTrash() a unique name for the trash.js to avoid confusions with the same function in files.js

Ajax loading is not supported yet for public files view.
This fix disabled the history API, ajax loading and ajax directory
switch in public mode until it is implemented properly.

Now correctly reinitializing the breadcrumb drop zone after ajax
navigation.

This also fixes dropping onto the "files" app icon.

Some apps like the files_trashbin app do not set a directory on its
"home" breadcrumb link.

This fix makes sure that the click event doesn't do anything in that
case and lets the browser open the link.

This fixes the "home" icon in the trashbin app which now correctly
reopens the files app.

The message for invalid private key was too long and didn't fit in the
notification box. This fix reduces the message to fit properly by
removing the extra information.

use 96x96 as 64x64 thumbnails in conflicts dialog, 64x64 looks very blocky ... maybe something is wrong there

use places/folder icon,
move link construction to JS,
only show icon on hover,
use 'searchresult' as css class name,
add filter/unfilter methods,
highlight searched files in current filelist
only filter when correct FileList is present

Using delegate might break apps that embed themselves in the files
container. When an app embeds itself and the user clicks a breadcrumb,
it will simply reload the whole browser page.

Frontend:
- The files app list now uses ajax calls to refresh the list.
- Added support the browser back button (history API).
- Added mask + spinner while loading file list

Backend:
- Added utility function in core JS for parsing query strings.
- Moved file list + breadcrumb template data code to helper
  functions
- Fixed some file paths in trashbin app to be similar to the files app