Add multiple service definition support

This change-set adds another key to the configuration decoding called
`services`, which is expected to be a list of service definitions. It
follows the established convention of only allowing one of the keys:
`service`, `check`, `services`. For every entry in the list it calls
the corresponding decode method and appends it to the Servics of the
resulting Config.

While a similar result could be achieved with changing the Services
member of the Config struct to have named mapstruct tag it lacks the
proper time conversions provided by DecodeServiceDefinition.
Merge pull request #431 from soundcloud/xla-multiple-service-definitions

Add multiple service definition support
agent: test config as a whole in services test
agent: add support for multiple checks and config mixing
website: update docs for multiple checks in config
Redirect old WebUI downloads page to new one

There are currently a number of sites on the Internet that link to the old
downloads_web_ui.html page, including some popular blog posts. Since the WebUI
has been moved onto the Consul page itself, these links are now broken.

This commit adds a 301 (to preserve SEO) redirect from the old page to the new
one.
Merge pull request #436 from hashicorp/sethvargo/redirect_web_ui_downloads

Redirect old WebUI downloads page to new one
Do not index "Jespen" code block

The word "Jespen" is one of our top keywords because it appears so many times
in the Jespen Testing page. This commit adds a comment to disable Google
indexing in that code block so we can better target keywords.
Merge pull request #435 from hashicorp/sethvargo/no_index

Do not index "Jespen" code block
Force a bundle update for rack-rewrite
website: fix JSON in multiple checks documentation
Merge pull request #433 from hashicorp/f-multi-checks

agent: add support for multiple checks and config mixing
website: fix download link for web UI in intro guide.
Merge pull request #441 from tomlanyon/master

website: fix download link for web UI in intro guide.
ACL doc clarification

Fixes #443
Rephrase
Merge pull request #444 from lra/acl_doc_clarification

Acl doc clarification
Add multiple recursor definition support
Fix missing arguments
Merge pull request #450 from ceh/fix-missing-arguments

Fix missing arguments