use email as account username in default
use email as account username in default

- Using email directly instead of hashing it.
  it is definitly equivalent things.
  Because 1:1 relation hash with email.
  Because cleaned_email in signup-form of
  account validate email as consist of characters
  that can be used as username.

- avoid try exception block when checking username.

Signed-off-by: Hiroshi Miura <ff6fb3ed059786151e736af13627c08d24e9f922@linux.com>

miurahr/symposion,miurahr/symposion