runner: add 'compile' operation

`bork compile $scriptname` will now output to STDOUT a script that contains all
the relevant parts of bork necessary to make $scriptname run without bork,
including $scriptname itself.  For example:

``` bash
bork compile foo.sh > build_foo.sh
scp build_foo.sh me@remotehost.com:build_foo.sh
ssh me@remotehost.com
./build_foo.sh status
```
you can pass an `--operation` argument with:

    bork compile $scriptname --operation=[status | satisfy]

and the operation argument will be baked into the script.  This is useful
for creating a vagrant provisioner, for example.
Merge branch 'compile'