webui: Only show volume name option for file/disks

It's not useful for other drivers.
Merge pull request #69 from vuntz/webui-volume-name

webui: Only show volume name option for file/disks
Fixes to SSL certificate generation

Several fixes, including:
 - do not recreate the certificate if it already exists
 - do not change permissions on directories that might be different than
   what we expect (code was assuming it was always
   /etc/<component>/ssl/{certs,private})
 - make private key non-readable by the world
webui: Some fixes related to SSL generation too

This includes:
  - really set insecure to true when generating certificate (it wasn't
    set in the json)
  - also make the path to certificate and key files disabled
webui: Fix string to be consistent

self-signed, instead of auto-signed.
webui: Set xxlarge class on file type inputs

For text input fields that take large amount of data (like a full file +
path), setting input-xxlarge class helps with getting a proper display
when using bootstrap.