Added haproxy sidecar in its most basic form

[cin]

Still a WIP

• [ ] Add appropriate liveness/readiness checks
• [x] Automatically send SIGHUP to haproxy process when haproxy.cfg is updated (watch CM in controller?)
• [x] Add dashboard for haproxy
• [x] Determine how the user is to provide VCL and how we default/configure the haproxy backends
• [ ] Optimize haproxy.cfg

[cin]

So far looks good, left a few comments. Also, do you plan on making a default haproxy config? We either need to do that or require users to reference a configmap with haproxy configs, also check if exists (or just fail if not?). Also not sure what would be a default config..

I think the only way we can make a default haproxy.cfg is if we templatize the DNS name or server lines. I'm not sure how generic we can make this. For that example, our default config would basically proxy SSL traffic for us (which is all we want). As long as the user can provide w/e config they need on top of that, is my biggest concern. I'm also fine w/requiring a configmap name. We could still use the proxy as example in that case. :)