reorder operations for consistency
factorize SNMP info update
factorize network info update
factorize specific object initialization
return directly, to reduce depth
rename variable for readability

'$class' is an object allowing to handle actual instances of this class.
rename variables for readability

- use plurals for list of items: $addresses is a list of address
- use singular for single items: $address is a single address
- use shorter name when there is no ambiguity: $address is enough, as
  there is no other kind of address as IP address in this scope
tidify calls to writeXML

And ensure usage consistency.
Merge branch 'master' of git+ssh://forge.fusioninventory.org/git/fusioninventory/fusioninventory-for-glpi

Conflicts:
	inc/communicationnetworkdiscovery.class.php
cosmetic: indentation fix
cosmetic: indentation fix
add support for SNMP timeout setting
drop useless deprecated CORE option

The agent doesn't handle it since a long time ago.