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

Fix #4876

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

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