#7 Improvement - Add option to allow disable or enable a item/discovery

[Levi Pereira]

Add a new attribute on <discovery>, <query> and <multiquery> to allow disable it. Something like enabled="false". Default value "true".</multiquery></query></discovery>

e.g: <discovery time="60" item="tablespaces.discovery" names="TABLESPACE_NAME" enabled="false"></discovery>

This will help us in fast way to disable a item instead need to remove or comment it on XML files.