Updated Arabic translation
Updated Lithuanian translation
Assamese translation reviewed
Assamese translation reviewed
make the progresss dialog modal when not in batch mode
make the "encrypt header" option insensitive if no password is specified
set a fixed title for the progress dialog
add a left padding to the "other options"
when canceling an operation kill all the sub-processes as well

create a new process group and kill the process group to stop the
operation.
Updated Russian translation
Updated Greek translation
removed unused functions
FrCommand: set the filename before each call to fr_command_* functions

this change will allow the command to use a different filename from
the one pointed to by the local_copy attribute.
removed wrong call to fr_process_start
added a cancellable object to some GIO functions
use local_copy instead of command->filename to check file existence

the command->filename == local_copy assumption will not be true
in the future
renamed tmp_archive to old_archive

to improve code readability
removed useless call to fr_archive_stoppable

it is called again in fr_archive_add
improved readability of code
allow the user to cancel addition and deletion of files

to make these operations stoppable the archive is copied in a
temporary directory and if the user cancel the operation the
temporary directory is deleted and the original file is preserved.