Use username in place of empty or nil display_name on user
Use username in place of empty or nil display_name on user

- Fixes bug 2-empty-display_name-property-in-user-model-not-handled-properly

silliemunkie/cpsprojectmanagement,silliemunkie/cpsprojectmanagement,kakra/railscollab,UWC4C/Railscollab,UWC4C/Railscollab,rajeshrsmail/railscollab,rajeshrsmail/railscollab,kakra/railscollab