Also, add a test case.

* add nginx to load balancing nav menu and fix bullets

* fill out nginx lb guide

* formatting

* change Nginx to NGINX

* add step to verify load balancer config

* update docker image and web app output

* change Nginx to NGINX in main load balancing page

* modify change signal to SIGHUP and add else condition in template stanza to prevent nginx from crashing when no services are available to load balance

* add note about external load balancer

* clarifications and link to reference architecture

As the angle bracket invocation RFC says:

> There is no dedicated syntax for passing an "else" block
> directly. If needed, that can be passed using the named
> blocks syntax.

https://github.com/emberjs/rfcs/blob/master/text/0311-angle-bracket-invocation.md#block

Unfortunately, using a contextual component doesn’t help as
the yield inside that component will still result in content
rendering that would show when the source isn’t empty. So
we decided to change the interface so you have to check
whether the source is empty before using it, which aligns with
how list-table works.

docs: job volume spec tasks source, not config > source

docs: fix links to connect

driver/docker: ensure that defaults are populated for dangling containers config

Added version requirement to new feature guides

docs: Added alert to mainpage for new 0.10

Merge 0.10.0 release branch back into master

docs: remove link to 0.10.0-rc1

Co-Authored-By: Michael Schurter <mschurter@hashicorp.com>

docs: bump to Nomad 0.10.0

This reverts commit 482862e6.

Fixes #6375

Intentionally omitted IPs prior to 0.10.0 release to minimize changes
and risk.

client: expose group network ports in env vars

Fixes #6375

Intentionally omitted IPs prior to 0.10.0 release to minimize changes
and risk.

Update link to new blog

Looks like we may need to pass default literal at each layer to be able,
so defaults are set properly.

docker: periodically reconcile containers

Other labels aren't strictly necessary here, and we may follow up with a
better way to customize.

Use golang 1.12.12

driver.SetConfig is not appropriate for starting up reconciler
goroutine.  Some ephemeral driver instances are created for validating
config and we ought not to side-effecting goroutines for those.

We currently lack a lifecycle hook to inject these, so I picked the
`Fingerprinter` function for now, and reconciler should only run after
fingerprinter started.

Use `sync.Once` to ensure that we only start reconciler loop once.

Append the Docker image sha to the Envoy image to ensure users default
to using the version that Nomad was tested against.