Removed attempt to get attached invoice object for AR and improved invoice batch item descriptions
Fix i18n and add t() to utils.py

To prevent  UnicodeDecodeErrors, do this to all strings that are not
automatically translated:

from bika.lims import _
from bika.lims.utils import t
some_string = t(_("English String"))
Merge pull request #1218 from bikalabs/fix/invoicebatch-create

Fixed invoice batch creation
Moved utils into a directory
Sending specific values for AR creation processForm and moved analyses calculations closer to where they are used