core, engine, webadmin: Initial support for alternative architectures

* This change introduces a field indicating the target architecture of
  the VM, Templates and clusters present in the engine.
* This field is used in architecture related code in order to introduce
  support for the IBM POWER systems.
* The commands responsible for adding and updating these entities were
  modified, along with the REST API, the DAOs, the database and the
  frontend.
* For VM and Templates, the architecture field is being inherited from
  the cluster.

Change-Id: I1ecd642e2bc05067d55884c948bdaeb6e7838c26
Signed-off-by: Vitor de Lima <vitor.lima@eldorado.org.br>
Signed-off-by: Leonardo Bianconi <leonardo.bianconi@eldorado.org.br>
Signed-off-by: Gustavo Pedrosa <gustavo.pedrosa@eldorado.org.br>