Merge commands/* into one control script

Right now there are a number of scripts like `start_slave.py`, `start_master.py` and so on. Merge them into one `antnest` script which does all of the actions above.

It could be used e.g. like this:

``` bash
antnest start-slave -p 33311
```

OR

``` bash
antnest create-job -j jobs/reverse_strings.py
```
