[PVE-User] Proxmox provided container system appliances updated

[Thomas Lamprecht]

Hi,

At the end of last week we updated the container system appliances,
hosted on http://download.proxmox.com/images/
As previously, they are available to download through the Proxmox VE
webUI storage content panel.

Here a quick overview of what changed:

New:
* Ubuntu Artful (17.10)
* Alpine Linux 3.6
* Alpine Linux 3.7
* Fedora 26
* Fedora 27
* openSUSE 42.3

Updated (point release or rolling release):
* Debian Stretch (9.0 -> 9.3)
* Centos 7 (04 May 2017 (7.3) -> 12 Dec. 2017 (7.4))
* Arch Linux (04 July 2017 -> 12 Dec. 2017)
* gentoo (03 May 2017 -> 11 Dec. 2017)

Removed (EOL):
* Fedora 24
* Alpine Linux 3.3

Note: Removals are done from the appliances index, they may be still
downloaded manually, if needed.

cheers,
Thomas