added 'exec:{}' option to pass options to ssh exec command. configurable...

... in briefing or option to transport.[exec|sudo]


Added the ability to pass options to ssh.exec command from either briefing or when running command.
Needed this to enable pty:true when executing certain sudo commands like 'apt-get install'

one time: 
```
transport.sudo('apt-get install sompackage', {exec:{pty:true}})
```

globally:
```
{
   destinations: {
      'dev' : {
          host:"dev.example.com"
          password:"somepassword"
          exec:{
             pty:true
          }
      }
}
```