delete old docs (#327)

* delete old docs

* new docs

docs/pages/cli/exec.md

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+# Exec
+
+```bash
+autorestic exec [-b, --backend]  [-a, --all] <command> -- [native options]
+```
+
+This is a very handy command which enables you to run any native restic command on desired backends. Generally you will want to include the verbose flag `-v, --verbose` to see the output. An example would be listing all the snapshots of all your backends:
+
+```bash
+autorestic exec -av -- snapshots
+```
+
+With `exec` you can basically run every cli command that you would be able to run with the restic cli. It only pre-fills path, key, etc.