Create an LWRP for host group creation

Namespace library to prevent possible conflicts with 3rd party libs

Create with_connection method that executes a block in the context of a
zabbix connection
Rename library file
Adds simple host registration LWRP

Fixes type in providers/host_group.rb
fix unless..elsif
fix actions
zabbixapi do the right job
try to fix group_id
fix missing new_ressource
Refactors group creation in host lwrp
Fixes bad attribute name
Merge branch 'new_agent-registration' of github.com:Youscribe/zabbix into new_agent-registration

Conflicts:
	libraries/zabbix_connection.rb
	providers/host.rb
	recipes/agent_registration.rb
	resources/host.rb
Bad merge on chef_zabbix_error.rb