sshd_config: establish default values in overlay

Add default,secure values for /etc/ssh/sshd_config via overlay.

Fixes #317
Fixes #262

kernel: 4.15.0-72.81

build: go 1.13

also bumped deps:
- github.com/mattn/go-isatty
- github.com/rancher/mapper
- github.com/sirupsen/logrus
- github.com/urfave/cli
- golang.org/x/crypto
- golang.org/x/sys

Fixes #305

doc: fix http_proxys typo

cli: refactor k3os commands into single multi-call binary

- `os-config` -> `k3os install`
- `ccapply` -> `k3os config`
- `rc.init` -> `k3os rc`

project: add bug report and feature request templates

Partially addresses #299

scripts/run-qemu: enable host qga socket by default

With this change, invoking `scripts/run-qemu` with this following arguments will result in the activation of qemu-guest-agent in the guest VM:
- `k3os.mode=live`
- `'boot_cmd="echo GA_PATH=/dev/vport0p1>/etc/conf.d/qemu-guest-agent"'`

Unless the `$STATE_DIR` envvar is overridden, the `qga.sock` will be in the `build/state/k3os-$TAG` directory.
e.g.
`echo '{"execute":"guest-get-osinfo"}' | socat unix-connect:/tmp/qga.sock stdout`

refactor how we build linuxkit bits

- upstream metadata is pulled on from v0.7 (latest release tag)
- forked rc.init has been plopped down in ./cmd/rc.init/

Prepares for #202
Prepares for #294

tooling: toolbox, rng-tools, htop, qemu-guest-agent

Includes:
- rng-tools by @zimme #270
- htop by @zimme #269
- toolbox by @bhale #257

Fixes #291
Fixes #265
Fixes #256

persist /etc/rancher/node across reboots

Fixes #289

 k3s: v1.0.0

k3s: v1.0.0-rc6

k3s: v1.0.0-rc5

kernel: 4.15.0-70.79

Fixes #278

ccapply: add label with the value of k3os.mode

If the `k3os.mode` (read from /var/run/k3os/mode) is not empty then add
node-label `k3os.io/mode=${k3os.mode}`.

rootfs: move k3s symlinks out of overlay

Removes k3s symlink and sub-command/reexec symlinks to it from `overlay/sbin`.
These symlinks are now all declared in the rootfs Dockerfile.

This should fix and issue with wranger generation code failing on the symlinks pointing to nowhere on module copy.

Fix type-o and structure

add ctr symlink (bundled as k3s sub-command) to /usr/sbin

- live cd boot
  `./scripts/run-qemu k3os.mode=live`

- silent install
  `DISK_NAME=test.img ./scripts/run-qemu k3os.password=rancher k3os.mode=install k3os.install.silent k3os.install.device=/dev/vda`

- run installed vm
  `DISK_NAME=test.img ./scripts/run-qemu k3os.password=rancher`

- recover installed vm
  `DISK_NAME=test.img ./scripts/run-qemu k3os.password=rancher k3os.mode=live`

Adding packer templates for vSphere