Services should not require a port

Fixes #3673

Add Spark configuration properties for ACL token and namespace

Skip tests that require root when not root

Add Spark configuration properties for ACL token and namespace. Remove spark.nomad.job property (deprecated in favor of spark.app.id).

Update eval modify index as part of plan apply.

Minor fixes and additions to Resources page

Travis: Lock down nodejs version

The new Travis Trusty image uses node 8 (latest LTS) as the default.
Node 8 is incompatible with some modules used for the UI.

Update template.html.md Vault template example

The change updates the Vault example within the Environment Variables section to use the `.value` notation rather than the `.key` notation. This is because the example is calling a specific secret key and populating an env var with this; meaning the value of the secret is required over the value.

Also skip Chown on allocdir migration on Windows and when non-root.
Windows doesn't support it, and it will always fail as a non-root user.

Fix minor formatting issue on Docker docs page

Unbold hyperlinks on Resources page

chown $GOPATH for vagrant user

Use the Service.Hash() method in agent service ids

Fix for rpc_upgrade_mode

The allocID and taskName parameters are useless for agents, but it's
still nice to reuse the same hash method for agent and task services.
This brings in the lowercase mode for the agent hash as well.