Fix minor typo in cli_helper. (Expresion vs Expression)

Hi everyone,

this pull request fixes a minor typo in cli_helper.rb. The word 'Expression' misses a 's' :-). 

    [matthias@one ~]$ onetemplate list  -f ID
      ID USER            GROUP           NAME                                REGTIME
    Expresion 'ID' incorrect
    [matthias@one ~]$ 


best regards,
Matthias