Fix various error messages and conditions in "git branch", e.g. we
advertised "branch -d/-D" to remove one or more branches but actually
implemented removal of zero or more branches---request to remove no
branches was not rejected.

* nd/branch-error-cases:
  branch: let branch filters imply --list
  docs: clarify git-branch --list behavior
  branch: mark more strings for translation
  branch: give a more helpful message on redundant arguments
  branch: reject -D/-d without branch name