Updated account settings for push notifications
Updated account settings for push notifications

Doc for https://mattermost.atlassian.net/browse/PLT-3399, https://mattermost.atlassian.net/browse/PLT-3462, and https://mattermost.atlassian.net/browse/PLT-3461.
funkyfuture/docs,funkyfuture/docs,funkyfuture/docs,funkyfuture/docs