Chore: Hugo upgrade (#17494)

* Fix: Upgrade hugo wip

* Chore: Rename index to _index for latest hugo

* Chore: Use relative refs, no starting slash

* Feat: Add possibility to mount layouts from grafana.org project

docs/sources/installation/_index.md

@@ -0,0 +1,23 @@
++++
+title = "Installation"
+description = "Install guide for Grafana"
+keywords = ["grafana", "installation", "documentation"]
+type = "docs"
+aliases = ["installation/installation/", "v2.1/installation/install/", "install"]
+[menu.docs]
+name = "Installation"
+identifier = "installation"
+weight = 1
++++
+
+## Installing Grafana
+
+- [Installing on Debian / Ubuntu](debian)
+- [Installing on RPM-based Linux (CentOS, Fedora, OpenSuse, RedHat)](rpm)
+- [Installing on Mac OS X](mac)
+- [Installing on Windows](windows)
+- [Installing on Docker](docker)
+- [Installing using Provisioning (Chef, Puppet, Salt, Ansible, etc)](provisioning)
+- [Nightly Builds](https://grafana.com/grafana/download)
+
+