Use Pulsar._createTask throughout the application

Depends on #31
As discussed
- add pulsar conf repo options directly into args.pulsarOptions. User doesn't have the ability to set pulsarOptions from web or socket interface.
- use only `Pulsar._createTask` for all pulsar commands (also for getAvailableTasks())
- remove PulsarExec.setPulsarOption()


It would be much easier to bind to task events instead of process ones.
```js
task.on('close', function(err) {
  task.output // gets output
  return callback(err);
});
```

`err` might not be actually implement on PulsarTask, but I think it should. Wdyt @vogdb ?