Docs/kubernetes-on-baremetal: Rename baremetal to matchbox
Docs/kubernetes-on-baremetal: Rename baremetal to matchbox

Upstream of dghubbe's https://github.com/coreos-inc/coreos-pages/pull/1241
Fix broken link to Ignition docs
Make links reference-style

coreos/coreos-kubernetes,joshix/coreos-kubernetes,joshix/coreos-kubernetes,coreos/coreos-kubernetes