shell: Disable chunk size for RAID 1

Disable the selectpicker for RAID 1
Show the text "0 KB" for RAID 1
Set the chunk size to 0 when creating RAID devices

Fixes #1071
I think you need to 'refresh' the selectpicker, like so:
```
$('#create-raid-chunk').prop('disabled', ...).selectpicker('refresh')
```

Selectpicker API: http://silviomoreto.github.io/bootstrap-select/