Change of some UI stuff

- Remove assignee part in the 'import' area

  Use of 'Import' is used to create new 'Open' packages quickly and set their
  versions. The assignees are not known at this point.

- Add field for 'Version' in the Tasks.

  The version is needed to set the 'tagversion' parameter when we create a new
  bug in Bugzilla.

  The current way of doing it in the bz_bugs_controller.rb incorrectly sets the
  'tagversion' to the candidate tag.

- Set the version in the package to be the same version as specified in the
  'Import' field.