Default user for backup has been changed from `backup` to `borg`.

User `backup` is now a system user on Debian testing. After each upgrade
involving related pacakges (pam?) our `backup` user is overwritten by
the Debian system one.

Also the default repositories folder has been changed from
`/home/backup/repos` to `/home/borg/repos`.

To adapt our existing infrastructure, after moving all the repos for all
the servers, some metadata (cache probably) need to be updated.

This update is done automatically when creating a new archvie if we set
the environment variable `BORG_RELOCATED_REPO_ACCESS_IS_OK` to `yes`.

Our backup script has been adapted to set this env variable to `yes`,
then we run a first run of backup on each host, afterwards we changed
the env variable in all backup scripts again to `no`.

new php packages required added

read password from config file instead of generating one new every time

Plus some php cache tunings

http external web services are monitored as separeted host

To avoid excessive consumption of UDP port that seems to be detected
and blocked by SIAF upstream firewall.

Only loopback relay is permitted, so the only TURN Topology allowed
is:

Forward:
Client 1 <--TURN--> (udp/88) Server <--RTP--> Server (udp/88) <--TURN--> Client 2

Topologies like:

Client 1 <--TURN--> (udp/88) Server (udp/>10000) <--RTP--> Client 2

Are not allowed.