Improvement for New > Network View related to private network

[Darkbeldin]

The goal of this is to improve the New > Network view in relation with private network creation
Here are the points that need to be addressed:

• There is no distinction between single host private network and cross-host private network.
  
  XCP-Center view for reference.
• Single host private network should not allow to select a PIF.
• Cross-host private network need SDN-controller plugin to be activated also limited to XOA premium.
• Cross-host private network should not be possible if allowed IP are activated on a VM in the pool.