Disable an Installation

under the BASIC use cases that we are going to initially support http://aerogear.org/docs/specs/aerogear-server-push/

it says disabling of specific installations. It doesn't look like there is a field on the Installation model that allows for this.

I'm guessing all we need is a boolean and default it to true( enabled )

then we probably just need to update our "queries" to look at this field when getting the list to send to