New model and abstraction classes to manage domain GPOs
Fix comments and GPO data table attributes
Give support to custom proxied redirections

+ Give support to custom proxied redirections to provide local HTTP
  servers from Zentyal Remote using /etc/zentyal/remoteservices_redirections.yaml
Remove proxy redirections file if not longer used
Use a more custom way to set proxy redirections
Add new function klist to libauthen-krb5-easy perl
Add new kerberos authentication helper class
Fixing absolute URLs rewrite rule pattern
Redirect to / from /ebox using remote access to avoid blank page

* This happens as /ebox does nothing when the user is already identified.
* Redirect to / when this happens
Add more contructor parameters to AuthKrbHelper

Now the principal can be specified by domain SID, domain RID or samAccountNAme.
The realm is also an optional parameter, readed from the GeneralSettings model
if not specified.
Remove useless parameters
Basic GPO UI and create, edit and delete ops
Merge branch 'master' into scabrero/samba-gpos
Fix LdbObject and childs constructors
Fix GPO deletion
Fix GPO edition
WIP in GPO software deployment
Merge branch 'master' into scabrero/samba-gpos
Set dependency version on libauthen-krb5-easy
Fix precondition on GPOs model

GPOs model must not be usable until domain is provisioned