Missing translations and i18n support

General

Date utils

• The error received when entering an invalid date (e.g. for a milestone) is not translatable:

  Error: Invalid Date
  
  "18.02.2010" is an invalid date, or the date format is not known. Try "MM/DD/YYYY" instead.
  

Admin

• When adding already existing enum, it's type is not translatable in the error message.

Configuration

• The title "Configuration Error" is not translatable.

To recreate the problem I changed this in trac.ini:

[attachment]
max_size = ddd262144

And tried to upload an attachment.