Add instance_port and permissions to the Application resource, allow updating applications.

[yoo]

This PR adds instance_port and permissions to the application resource schema.
In addition it implements the the resourceApplicationUpdate function to allow terraform to update a spinnaker application.

This PR includes a dirty hack, which I'm happy to fix if someone knows how.
When adding permissions to an application, on create, the permissions are not visible to
the Gate API and terraform receives an HTTP 403 when trying to read the application.
Terraform needs to wait until the cache is refreshed, but it dose not know how long (cache timeout).
I didn't found a way to force a cache invalidation or refresh the cache before reading the application.

[ethanfrogers]

@yoo sorry for the massive delay here. Let me do some testing with this. Is there any reason to favor this approach vs using something like this?

[nicholasgcoles]

@ethanfrogers @yoo anybody need some help on this?

[KhadijaBenAmmar]

Does this PR is going to be merged?