webadmin: Selection of incompatible templates

This change filters the displayed templates in the "New Pool" and
"New VM" dialogs to show only the ones that are compatible with the
selected cluster.

Change-Id: I2acd521718c8c6d4c27ffce20628b8d096dc4f1a
Signed-off-by: Vitor de Lima <vitor.lima@eldorado.org.br>
Signed-off-by: Gustavo Pedrosa <gustavo.pedrosa@eldorado.org.br>