Feature/realm

This branch adds the possibility to use the RADIUS realm to filter which authentication source(s) to use to retrieve the normal VLAN.

Update:
Description
---------------
This branch manage the realm in packetfence:
Add a file in radius configuration to set the realm and the options
Use or no the stripped user to match authentication source
Add a portal filter to match on the realm

Impacts
-----------
This will change the way to deal with the authentication sources and the realm hasn´t been defined then we will receive username attribute like that (user@domain.ca or DOMAIN\User) in packetfence.

Delete branch after merge
-------------------------
YES 


Already defined previously