Allow overriding an image's entrypoint in Docker

Fixes https://github.com/hashicorp/nomad/issues/2219

Add an option to add and drop capabilities in the Docker driver

Client/Server TLS dynamic reload

Always advertise driver IP when in driver mode

Allow `.` in Environment Variable Names

Includes hashicorp/go-envparse#2

From [https://github.com/appc/spec/blob/master/spec/aci.md](https://github.com/appc/spec/blob/master/spec/aci.md):

>environment (list of objects, optional) represents the app's environment variables (ACE can append). The listed objects must have two key-value pairs: name and value. The name must consist solely of letters, digits, and underscores '_' as outlined in IEEE Std 1003.1-2008, 2016 Edition, with practical considerations dictating that the name may also include periods '.' and hyphens '-'. The value is an arbitrary string. These values are not evaluated in any way, and no substitutions are made.

Dotted environment variables are frequently used as a part of the Spring Boot pattern. (re: ZD-6116)

This PR specifically doesn't address the conversion of hyphens (`-`) due to an issue with rkt [[Nomad GH # 2358]](https://github.com/hashicorp/nomad/issues/2358).

Docs: Add command consul agent & fix nomad command

`sudo` is required to enable other drivers like rkt and java while the
`-dev` flag enables the agent to run in a standalone mode.

Add Autopilot feature from Consul

Component-ize UI for placement failures

1. Extra whitespace
2. Remove redundant code
3. Remove redundant markup from test
4. placement-failure should be used as an inline component
5. Prefer `assign` polyfill
6. Use new `@ember' org style imports

1. cleanWhitespace > /test/utils/clean-whitespace.js
2. Missd the data-test attribute for placement failures in previous
conflict

1. Simple move of placement-failures template code to a component
2. Start adding integration tests - hit `inc` surprise

Make example service name make sense

For people not using driver networks these log lines would just be
confusing.

Related to #3681

If a user specifies an invalid port *label* when using
address_mode=driver they'll get an error message about the label being
an invalid number which is very confusing.

I also added a bunch of testing around Service.AddressMode validation
since I was concerned by the linked issue that there were cases I was
missing. Unfortunately when address_mode=driver is used there's only so
much validation that can be done as structs/structs.go validation never
peeks into the driver config which would be needed to verify the port
labels/map.

Fixes #3681

When in drive address mode Nomad should always advertise the driver's IP
in Consul even when no network exists. This matches the 0.6 behavior.

When in host address mode Nomad advertises the alloc's network's IP if
one exists. Otherwise it lets Consul determine the IP.

I also added some much needed logging around Docker's network discovery.