dashboard: CPU, memory, diskIO and traffic on the footer (#15950)

* dashboard: footer, deep state update

* dashboard: resolve asset path

* dashboard: prevent state update on every reconnection

* dashboard: fix linter issue

* dashboard, cmd: minor UI fix, include commit hash

* dashboard: gitCommit renamed to commit

* dashboard: move the geth version to the right, make commit optional

* dashboard: memory, traffic and CPU on footer

* dashboard: fix merge

* dashboard: CPU, diskIO on footer

* dashboard: rename variables, use group declaration

* dashboard: docs

vendor/github.com/elastic/gosigar/README.md

@@ -0,0 +1,57 @@
+# Go sigar [![Build Status](https://travis-ci.org/elastic/gosigar.svg?branch=master)](https://travis-ci.org/elastic/gosigar) [![Build status](https://ci.appveyor.com/api/projects/status/4yh6sa7u97ek5uib/branch/master?svg=true)](https://ci.appveyor.com/project/elastic-beats/gosigar/branch/master)
+
+
+## Overview
+
+Go sigar is a golang implementation of the
+[sigar API](https://github.com/hyperic/sigar).  The Go version of
+sigar has a very similar interface, but is being written from scratch
+in pure go/cgo, rather than cgo bindings for libsigar.
+
+## Test drive
+
+    $ go get github.com/elastic/gosigar
+    $ cd $GOPATH/src/github.com/elastic/gosigar/examples/ps
+    $ go build
+    $ ./ps
+
+## Supported platforms
+
+The features vary by operating system.
+
+| Feature         | Linux | Darwin | Windows | OpenBSD | FreeBSD |
+|-----------------|:-----:|:------:|:-------:|:-------:|:-------:|
+| Cpu             |   X   |    X   |    X    |    X    |    X    |
+| CpuList         |   X   |    X   |         |    X    |    X    |
+| FDUsage         |   X   |        |         |         |    X    |
+| FileSystemList  |   X   |    X   |    X    |    X    |    X    |
+| FileSystemUsage |   X   |    X   |    X    |    X    |    X    |
+| LoadAverage     |   X   |    X   |         |    X    |    X    |
+| Mem             |   X   |    X   |    X    |    X    |    X    |
+| ProcArgs        |   X   |    X   |    X    |         |    X    |
+| ProcEnv         |   X   |    X   |         |         |    X    |
+| ProcExe         |   X   |    X   |         |         |    X    |
+| ProcFDUsage     |   X   |        |         |         |    X    |
+| ProcList        |   X   |    X   |    X    |         |    X    |
+| ProcMem         |   X   |    X   |    X    |         |    X    |
+| ProcState       |   X   |    X   |    X    |         |    X    |
+| ProcTime        |   X   |    X   |    X    |         |    X    |
+| Swap            |   X   |    X   |         |    X    |    X    |
+| Uptime          |   X   |    X   |         |    X    |    X    |
+
+## OS Specific Notes
+
+### FreeBSD
+
+Mount both `linprocfs` and `procfs` for compatability. Consider adding these
+mounts to your `/etc/fstab` file so they are mounted automatically at boot.
+
+```
+sudo mount -t procfs proc /proc
+sudo mkdir -p /compat/linux/proc
+sudo mount -t linprocfs /dev/null /compat/linux/proc
+```
+
+## License
+
+Apache 2.0