DB migration - new fields

invite (renamed):
id_sender -> sender_id
id_idea -> idea_id
id_receiver -> receiver_id

user:
bio

idea_link:
id
user_id
title
url
Models prepared for migration

Special mention - BaseInvite:
idSender -> senderId
id_sender -> sender_id
idIdea -> ideaId
id_idea -> idea_id
idReceiver -> receiverId
id_receiver -> receiver_id
SqlBuilder modified for DB migration
-user now returns bio variable
-idea now returns link array
A slight fix for idea_link