Feature/filter getvcpe

 Filter getVCPENetworkById and getAllVCPENetworks with AclManager.

getVCPENetworkById launches an exception if access to specified vcpe is denied for currently authenticated user.
getAllVCPENetworks filters the list of returned VCPEs garanting that only vcpes currently authenticated user has acess to are returned.

These methods make uso af ACLManager to check desired resource is accessible for currently authenticated user.

This patch includes a small refactor of VCPENetworkManager class.