Feature: fqdn value for assetname support option

[g-bougard]

As pointed out in Changes file:

* Feature: Update support assetname-support as option for agent on most unix
  if 1 (the default), the short hostname is used as asset name
  if 2, the as-is hostname (can be fqdn) is used as asset name
  if 3, the fqdn hostname is used as asset name
  this feature does not apply on MacOS or Windows
  this feature now works for remote ssh and for option 3, it requires perl installed
  on targeted computer and perl mode enabled on defined remote.
* Feature: Make assetname-support option also works to compute agent deviceid when
  unknown

IMHO this is a better answer than forcing every one to use fqdn as proposed in #535.

It also makes the option working for remoteinventory task.

[g-bougard]

Hi @po1vo

can you take a look to this PR as replacement candidate to #535 ?

[g-bougard]

As a side note, I udpated documentation to include assetname-support and reflect this PR:
https://glpi-agent.readthedocs.io/en/latest/configuration.html#assetname-support

[po1vo]

can you take a look to this PR as replacement candidate to #535 ?

Looks good! Thanks.