New model and abstraction classes to manage domain GPOs
Fix comments and GPO data table attributes
Add new function klist to libauthen-krb5-easy perl
Add new kerberos authentication helper class
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
Extract keytab after authentication failure

If the password of the user has changed, the extracted keytab gets out
of sync. After a auth failure, extract again and try to authenticate
with the new one.
WIP on Group Policy: Scripts extensions
Implement singleton for AuthKrbHelper
New class EBox::Samba::SmbClient

Extends the Filesys::SmbClient to add kerberos authentication using the
EBox::Samba::AuthKrbHelper and a new method to read a full file
Use new EBox::Samba::SmbClient class