Images on public sharing get downscaled to increase use experience - this will speed up loading time

- adding keep aspect to core/ajax/preview.php
- remove duplicate method Preview::show()
- no more hard coded mimetype of preview
- remove .png from the preview urls
- keep old route preview.png for backwards compatibility
- aspect preserving previews are now cached

reintroduce download button on public shares

[sharing] return the new name if a mount point was renamed

[sharing] fix rename of part files

Preserve keys when sorting parameters when generatings urls

Fixed too generic checkbox and link selectors

Show spinner for all files when deleting all

remove leftcontent and rightcontent CSS, no longer needed

Issue/8131 Fix emitting of filesystem related hooks

It turns out that the sharing dropdown is embedded into the table row
for some reason.

This fix makes use of a more specific selector for the checkboxes and
file name links to make sure it doesn't spill into any other potential
elements like the sharing dialog.

fix shouldEncrypt() method and improved decryptAll() unit tests

Handle return values better from Filesystem::getMountBy*

after being uploaded in .part files

Fix #8131

The write-hook also is triggered for created files

Fix #8131

do not check 'remember' log in by default

Update 3rdparty

Fixes login / logout when HTTP Basic Headers are avilable.

Update outdated comment

Infinite scrolling for files app

remove preview office fallback as it makes too much trouble and generates inacceptable results