Download Action

A new feature requiring lftp installed. It assembles an lftp mirror
command to download all changes from the FTP server into your current
working tree.

It deletes untracked files. Ideas how to tackle this:
- Accept it. Download is supposed to mirror. (I guess not.)
- Check for untracked files and throw an error before downloading. (My
  favourite.)
- Stash everything away and restore it after downloading. (Does too
  much. Could confuse. Could create a conflict.)
Abort download on untracked files.
Adding Dan Rench as author
Merge branch 'download' of github.com:git-ftp/git-ftp into develop

Conflicts:
	git-ftp
	tests/git-ftp-test.sh