file-roller ui and string changes

[Paolo Bacchilega <paolo bacchilega libero it>]

Hello,

file-roller has changed the UI of the new archive dialog adding a "other 
options" button to view advance create options, and now there is a help 
button in the create dialog used when creating an archive with the file 
manager contextual menu.

Also the user's manual has been updated by me, and it would be a good 
thing if some of you take a look at it.

Thanks,

Paolo.