WIP: sketch solution for logrotate and other stuff

This code isn't tested and probably not working, but wanted to sketch out a solution for embedding files destined for /etc/logrotate.d and other arbitrary places. Changes allow:

```
dist_dirs:
  - dir: server
    prefix: /usr/local/manta-frontend
```

instead of

```
dist_dir: server
prefix: /usr/local/manta-frontend
```

with the idea of adding additional stanzas such as:

```
  - dir: logrotate.d
    prefix: /etc/logrotate.d
```

Let me know what you think of the approach/naming/etc.

/cc @reprehensible @mantacode/systems-engineering