implement new 'zrepl status'

Primary goals:

- Scrollable output ( fixes #245 )
- Sending job signals from status view
- Filtering of output by filesystem

Implementation:

- original TUI framework: github.com/rivo/tview
- but: tview is quasi-unmaintained, didn't support some features
- => use fork https://gitlab.com/tslocum/cview
- however, don't buy into either too much to avoid lock-in

- instead: **port over the existing status UI drawing code
  and adjust it to produce strings instead of directly
  drawing into the termbox buffer**

Co-authored-by: Calistoc <calistoc@protonmail.com>
Co-authored-by: InsanePrawn <insane.prawny@gmail.com>

fixes #245
fixes #220

client/status/status_raw.go

@@ -0,0 +1,18 @@
+package status
+
+import (
+	"bytes"
+	"io"
+	"os"
+)
+
+func raw(c Client) error {
+	b, err := c.StatusRaw()
+	if err != nil {
+		return err
+	}
+	if _, err := io.Copy(os.Stdout, bytes.NewReader(b)); err != nil {
+		return err
+	}
+	return nil
+}